Elsevier QRcode Wechat

  • Manuscript Preparation

How to write your references quickly and easily

  • 3 minute read
  • 205.6K views

Table of Contents

Every scientific paper builds on previous research – even if it’s in a new field, related studies will have preceded and informed it. In peer-reviewed articles, authors must give credit to this previous research, through citations and references. Not only does this show clearly where the current research came from, but it also helps readers understand the content of the paper better.

There is no optimum number of references for an academic article but depending on the subject you could be dealing with more than 100 different papers, conference reports, video articles, medical guidelines or any number of other resources.

That’s a lot of content to manage. Before submitting your manuscript, this needs to be checked, cross-references in the text and the list, organized and formatted.

The exact content and format of the citations and references in your paper will depend on the journal you aim to publish in, so the first step is to check the journal’s Guide for Authors before you submit.

There are two main points to pay attention to – consistency and accuracy. When you go through your manuscript to edit or proofread it, look closely at the citations within the text. Are they all the same? For example, if the journal prefers the citations to be in the format (name, year), make sure they’re all the same: (Smith, 2016).

Your citations must also be accurate and complete. Do they match your references list? Each citation should be included in the list, so cross-checking is important. It’s also common for journals to prefer that most, if not all, of the articles listed in your references be cited within the text – after all, these should be studies that contributed to the knowledge underpinning your work, not just your bedtime reading. So go through them carefully, noting any missing references or citations and filling the gaps.

Each journal has its own requirements when it comes to the content and format of references, as well as where and how you should include them in your submission, so double-check before you hit send!

In general, a reference will include authors’ names and initials, the title of the article, name of the journal, volume and issue, date, page numbers and DOI. On ScienceDirect, articles are linked to their original source (if also published on ScienceDirect) or to their Scopus record, so including the DOI can help link to the correct article.

A spotless reference list

Luckily, compiling and editing the references in your scientific manuscript can be easy – and it no longer has to be manual. Management tools like Mendeley can keep track of all your references, letting you share them with your collaborators. With the Word plugin, it’s possible to select the right citation style for the journal you’re submitting to and the tool will format your references automatically.

Like with any other part of your manuscript, it’s important to make sure your reference list has been checked and edited. Elsevier Author Services Language Editing can help, with professional manuscript editing that will help make sure your references don’t hold you back from publication.

Professional Manuscript Translation

Why it’s best to ask a professional when it comes to translation

How-to-choose-a-Journal-to-submit-an-article

  • Research Process

How to Choose a Journal to Submit an Article

You may also like.

Guide to Crafting Impactful Sentences

A Guide to Crafting Shorter, Impactful Sentences in Academic Writing

Write an Excellent Discussion in Your Manuscript

6 Steps to Write an Excellent Discussion in Your Manuscript

How to Write Clear Civil Engineering Papers

How to Write Clear and Crisp Civil Engineering Papers? Here are 5 Key Tips to Consider

how write reference research paper

The Clear Path to An Impactful Paper: ②

Essentials of Writing to Communicate Research in Medicine

The Essentials of Writing to Communicate Research in Medicine

There are some recognizable elements and patterns often used for framing engaging sentences in English. Find here the sentence patterns in Academic Writing

Changing Lines: Sentence Patterns in Academic Writing

how write reference research paper

Path to An Impactful Paper: Common Manuscript Writing Patterns and Structure

how to write the results section of a research paper

How to write the results section of a research paper

Input your search keywords and press Enter.

  • PRO Courses Guides New Tech Help Pro Expert Videos About wikiHow Pro Upgrade Sign In
  • EDIT Edit this Article
  • EXPLORE Tech Help Pro About Us Random Article Quizzes Request a New Article Community Dashboard This Or That Game Popular Categories Arts and Entertainment Artwork Books Movies Computers and Electronics Computers Phone Skills Technology Hacks Health Men's Health Mental Health Women's Health Relationships Dating Love Relationship Issues Hobbies and Crafts Crafts Drawing Games Education & Communication Communication Skills Personal Development Studying Personal Care and Style Fashion Hair Care Personal Hygiene Youth Personal Care School Stuff Dating All Categories Arts and Entertainment Finance and Business Home and Garden Relationship Quizzes Cars & Other Vehicles Food and Entertaining Personal Care and Style Sports and Fitness Computers and Electronics Health Pets and Animals Travel Education & Communication Hobbies and Crafts Philosophy and Religion Work World Family Life Holidays and Traditions Relationships Youth
  • Browse Articles
  • Learn Something New
  • Quizzes Hot
  • This Or That Game New
  • Train Your Brain
  • Explore More
  • Support wikiHow
  • About wikiHow
  • Log in / Sign up
  • Education and Communications
  • College University and Postgraduate
  • Academic Writing
  • Research Papers

How to Cite a Research Paper

Last Updated: January 11, 2024 Fact Checked

This article was reviewed by Gerald Posner and by wikiHow staff writer, Jennifer Mueller, JD . Gerald Posner is an Author & Journalist based in Miami, Florida. With over 35 years of experience, he specializes in investigative journalism, nonfiction books, and editorials. He holds a law degree from UC College of the Law, San Francisco, and a BA in Political Science from the University of California-Berkeley. He’s the author of thirteen books, including several New York Times bestsellers, the winner of the Florida Book Award for General Nonfiction, and has been a finalist for the Pulitzer Prize in History. He was also shortlisted for the Best Business Book of 2020 by the Society for Advancing Business Editing and Writing. There are 9 references cited in this article, which can be found at the bottom of the page. This article has been fact-checked, ensuring the accuracy of any cited facts and confirming the authority of its sources. This article has been viewed 406,326 times.

When writing a paper for a research project, you may need to cite a research paper you used as a reference. The basic information included in your citation will be the same across all styles. However, the format in which that information is presented is somewhat different depending on whether you're using American Psychological Association (APA), Modern Language Association (MLA), Chicago, or American Medical Association (AMA) style.

Citation Help

how write reference research paper

  • For example: "Kringle, K., & Frost, J."

Step 2 Provide the year the paper was published.

  • For example: "Kringle, K., & Frost, J. (2012)."
  • If the date, or any other information, are not available, use the guide at https://blog.apastyle.org/apastyle/2012/05/missing-pieces.html .

Step 3 List the title of the research paper.

  • For example: "Kringle, K., & Frost, J. (2012). Red noses, warm hearts: The glowing phenomenon among North Pole reindeer."
  • If you found the research paper in a database maintained by a university, corporation, or other organization, include any index number assigned to the paper in parentheses after the title. For example: "Kringle, K., & Frost, J. (2012). Red noses, warm hearts: The glowing phenomenon among North Pole reindeer. (Report No. 1234)."

Step 4 Include information on where you found the paper.

  • For example: "Kringle, K., & Frost, J. (2012). Red noses, warm hearts: The glowing phenomenon among North Pole reindeer. (Report No. 1234). Retrieved from Alaska University Library Archives, December 24, 2017."

Step 5 Use a parenthetical citation in the body of your paper.

  • For example: "(Kringle & Frost, 2012)."
  • If there was no date on the research paper, use the abbreviation n.d. : "(Kringle & Frost, n.d.)."

Step 1 Start with the authors' names.

  • For example: "Kringle, Kris, and Jack Frost."

Step 2 List the title of the research paper.

  • For example: "Kringle, Kris, and Jack Frost. "Red Noses, Warm Hearts: The Glowing Phenomenon among North Pole Reindeer." Master's thesis."

Step 3 Provide the place and year of publication.

  • For example: "Kringle, Kris, and Jack Frost. "Red Noses, Warm Hearts: The Glowing Phenomenon among North Pole Reindeer." Master's thesis, Alaska University, 2012."

Step 4 Include any additional information necessary to locate the paper.

  • For example: "Kringle, Kris, and Jack Frost. "Red Noses, Warm Hearts: The Glowing Phenomenon among North Pole Reindeer." Master's thesis, Alaska University, 2012. Accessed at https://www.northpolemedical.com/raising_rudolf."

Step 5 Follow your instructor's guidance regarding in-text citations.

  • Footnotes are essentially the same as the full citation, although the first and last names of the authors aren't inverted.
  • For parenthetical citations, Chicago uses the Author-Date format. For example: "(Kringle and Frost 2012)."

Step 1 Start with the authors of the paper.

  • For example: "Kringle, Kris, and Frost, Jack."

Step 2 Provide the title of the research paper.

  • For example: "Kringle, Kris, and Frost, Jack. "Red Noses, Warm Hearts: The Glowing Phenomenon Among North Pole Reindeer.""

Step 3 Identify the paper's location.

  • For example, suppose you found the paper in a collection of paper housed in university archives. Your citation might be: "Kringle, Kris, and Frost, Jack. "Red Noses, Warm Hearts: The Glowing Phenomenon Among North Pole Reindeer." Master's Theses 2000-2010. University of Alaska Library Archives. Accessed December 24, 2017."

Step 4 Use parenthetical references in the body of your work.

  • For example: "(Kringle & Frost, p. 33)."

Step 1 Start with the author's last name and first initial.

  • For example: "Kringle K, Frost J."

Step 2 Provide the title in sentence case.

  • For example: "Kringle K, Frost J. Red noses, warm hearts: The glowing phenomenon among North Pole reindeer."

Step 3 Include journal information if the paper was published.

  • For example: "Kringle K, Frost J. Red noses, warm hearts: The glowing phenomenon among North Pole reindeer. Nat Med. 2012; 18(9): 1429-1433."

Step 4 Provide location information if the paper hasn't been published.

  • For example, if you're citing a paper presented at a conference, you'd write: "Kringle K, Frost J. Red noses, warm hearts: The glowing phenomenon among North Pole reindeer. Oral presentation at Arctic Health Association Annual Summit; December, 2017; Nome, Alaska."
  • To cite a paper you read online, you'd write: "Kringle K, Frost J. Red noses, warm hearts: The glowing phenomenon among North Pole reindeer. https://www.northpolemedical.com/raising_rudolf"

Step 5 Use superscript numbers in the body of your paper.

  • For example: "According to Kringle and Frost, these red noses indicate a subspecies of reindeer native to Alaska and Canada that have migrated to the North Pole and mingled with North Pole reindeer. 1 "

Community Q&A

SnowyDay

  • If you used a manual as a source in your research paper, you'll need to learn how to cite the manual also. Thanks Helpful 0 Not Helpful 0
  • If you use any figures in your research paper, you'll also need to know the proper way to cite them in MLA, APA, AMA, or Chicago. Thanks Helpful 0 Not Helpful 0

how write reference research paper

You Might Also Like

Cite the WHO in APA

  • ↑ https://askus.library.wwu.edu/faq/116659
  • ↑ https://guides.libraries.psu.edu/apaquickguide/intext
  • ↑ https://owl.purdue.edu/owl/research_and_citation/chicago_manual_17th_edition/cmos_formatting_and_style_guide/general_format.html
  • ↑ https://libanswers.snhu.edu/faq/48009
  • ↑ https://www.chicagomanualofstyle.org/tools_citationguide/citation-guide-2.html
  • ↑ https://owl.purdue.edu/owl/research_and_citation/mla_style/mla_formatting_and_style_guide/mla_in_text_citations_the_basics.html
  • ↑ https://morningside.libguides.com/MLA8/location
  • ↑ https://owl.purdue.edu/owl/research_and_citation/ama_style/index.html
  • ↑ https://research.library.oakland.edu/sp/subjects/tutorial.php?faq_id=187

About This Article

Gerald Posner

To cite a paper APA style, start with the author's last name and first initial, and the year of publication. Then, list the title of the paper, where you found it, and the date that you accessed it. In a paper, use a parenthetical reference with the last name of the author and the publication year. For an MLA citation, list the author's last name and then first name and the title of the paper in quotations. Include where you accessed the paper and the date you retrieved it. In your paper, use a parenthetical reference with the author's last name and the page number. Keep reading for tips on Chicago and AMA citations and exceptions to the citation rules! Did this summary help you? Yes No

  • Send fan mail to authors

Did this article help you?

how write reference research paper

Featured Articles

Ask Better Questions

Trending Articles

Everything You Need to Know to Rock the Corporate Goth Aesthetic

Watch Articles

Cook Fresh Cauliflower

  • Terms of Use
  • Privacy Policy
  • Do Not Sell or Share My Info
  • Not Selling Info

Don’t miss out! Sign up for

wikiHow’s newsletter

Logo for M Libraries Publishing

Want to create or adapt books like this? Learn more about how Pressbooks supports open publishing practices.

13.3 Creating a References Section

Learning objective.

  • Apply American Psychological Association (APA) style and formatting guidelines for a references section.

This section provides detailed information about how to create the references section of your paper. You will review basic formatting guidelines and learn how to format bibliographical entries for various types of sources. This section of Chapter 13 “APA and MLA Documentation and Formatting” , like the previous section, is meant to be used as a reference tool while you write.

Formatting the References Section: The Basics

At this stage in the writing process, you may already have begun setting up your references section. This section may consist of a single page for a brief research paper or may extend for many pages in professional journal articles. As you create this section of your paper, follow the guidelines provided here.

Formatting the References Section

To set up your references section, use the insert page break feature of your word-processing program to begin a new page. Note that the header and margins will be the same as in the body of your paper, and pagination continues from the body of your paper. (In other words, if you set up the body of your paper correctly, the correct header and page number should appear automatically in your references section.) See additional guidelines below.

Formatting Reference Entries

Reference entries should include the following information:

  • The name of the author(s)
  • The year of publication and, where applicable, the exact date of publication
  • The full title of the source
  • For books, the city of publication
  • For articles or essays, the name of the periodical or book in which the article or essay appears
  • For magazine and journal articles, the volume number, issue number, and pages where the article appears
  • For sources on the web, the URL where the source is located

See the following examples for how to format a book or journal article with a single author.

Sample Book Entry

Sample Book Entry

Sample Journal Article Entry

Sample Journal Article Entry

The following box provides general guidelines for formatting the reference page. For the remainder of this chapter, you will learn about how to format bibliographical entries for different source types, including multiauthor and electronic sources.

Formatting the References Section: APA General Guidelines

1. Include the heading References , centered at the top of the page. The heading should not be boldfaced, italicized, or underlined. 2. Use double-spaced type throughout the references section, as in the body of your paper. 3. Use hanging indentation for each entry. The first line should be flush with the left margin, while any lines that follow should be indented five spaces. Note that hanging indentation is the opposite of normal indenting rules for paragraphs. 4. List entries in alphabetical order by the author’s last name. For a work with multiple authors, use the last name of the first author listed. 5. List authors’ names using this format: Smith, J. C. 6. For a work with no individual author(s), use the name of the organization that published the work or, if this is unavailable, the title of the work in place of the author’s name.

7. For works with multiple authors, follow these guidelines:

  • For works with up to seven authors, list the last name and initials for each author.
  • For works with more than seven authors, list the first six names, followed by ellipses, and then the name of the last author listed.
  • Use an ampersand before the name of the last author listed.

8. Use title case for journal titles. Capitalize all important words in the title.

9. Use sentence case for all other titles—books, articles, web pages, and other source titles. Capitalize the first word of the title. Do not capitalize any other words in the title except for the following:

  • Proper nouns
  • First word of a subtitle
  • First word after a colon or dash

Set up the first page of your references section and begin adding entries, following the APA formatting guidelines provided in this section.

  • If there are any simple entries that you can format completely using the general guidelines, do so at this time.
  • For entries you are unsure of how to format, type in as much information as you can, and highlight the entries so you can return to them later.

Formatting Reference Entries for Different Source Types

As is the case for in-text citations, formatting reference entries becomes more complicated when you are citing a source with multiple authors, citing various types of online media, or citing sources for which you must provide additional information beyond the basics listed in the general guidelines. The following guidelines show how to format reference entries for these different situations.

Print Sources: Books

For book-length sources and shorter works that appear in a book, follow the guidelines that best describes your source.

A Book by Two or More Authors

List the authors’ names in the order they appear on the book’s title page. Use an ampersand before the last author’s name.

Campbell, D. T., & Stanley, J. C. (1963). Experimental and quasi-experimental designs for research. Boston, MA: Houghton Mifflin.

An Edited Book with No Author

List the editor or editors’ names in place of the author’s name, followed by Ed. or Eds. in parentheses.

Myers, C., & Reamer, D. (Eds.). (2009). 2009 nutrition index. San Francisco, CA: HealthSource, Inc.

An Edited Book with an Author

List the author’s name first, followed by the title and the editor or editors. Note that when the editor is listed after the title, you list the initials before the last name.

Dickinson, E. (1959). Selected poems & letters of Emily Dickinson. R. N. Linscott (Ed.). Garden City, NY: Doubleday.

The previous example shows the format used for an edited book with one author—for instance, a collection of a famous person’s letters that has been edited. This type of source is different from an anthology, which is a collection of articles or essays by different authors. For citing works in anthologies, see the guidelines later in this section.

A Translated Book

Include the translator’s name after the title, and at the end of the citation, list the date the original work was published. Note that for the translator’s name, you list the initials before the last name.

Freud, S. (1965). New introductory lectures on psycho-analysis (J. Strachey, Trans.). New York, NY: W. W. Norton. (Original work published 1933).

A Book Published in Multiple Editions

If you are using any edition other than the first edition, include the edition number in parentheses after the title.

Berk, L. (2001). Development through the lifespan (2nd ed.). Needham Heights, MA: Allyn & Bacon.

A Chapter in an Edited Book

List the name of the author(s) who wrote the chapter, followed by the chapter title. Then list the names of the book editor(s) and the title of the book, followed by the page numbers for the chapter and the usual information about the book’s publisher.

When creating a references section include the abbreviation

A Work That Appears in an Anthology

Follow the same process you would use to cite a book chapter, substituting the article or essay title for the chapter title.

When creating a references section include the abbreviation

An Article in a Reference Book

List the author’s name if available; if no author is listed, provide the title of the entry where the author’s name would normally be listed. If the book lists the name of the editor(s), include it in your citation. Indicate the volume number (if applicable) and page numbers in parentheses after the article title.

Capitalize proper nouns that appear in a book title while creating a references section

Two or More Books by the Same Author

List the entries in order of their publication year, beginning with the work published first.

Swedan, N. (2001). Women’s sports medicine and rehabilitation. Gaithersburg, MD: Aspen Publishers.

Swedan, N. (2003). The active woman’s health and fitness handbook. New York, NY: Perigee.

If two books have multiple authors, and the first author is the same but the others are different, alphabetize by the second author’s last name (or the third or fourth, if necessary).

Carroll, D., & Aaronson, F. (2008). Managing type II diabetes. Chicago, IL: Southwick Press.

Carroll, D., & Zuckerman, N. (2008). Gestational diabetes. Chicago, IL: Southwick Press.

Books by Different Authors with the Same Last Name

Alphabetize entries by the authors’ first initial.

When creating a freferences section, capitalize the first word of a subtitle

A Book Authored by an Organization

Treat the organization name as you would an author’s name. For the purposes of alphabetizing, ignore words like The in the organization’s name. (That is, a book published by the American Heart Association would be listed with other entries whose authors’ names begin with A .)

American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders DSM-IV (4th ed.). Arlington, VA: American Psychiatric Publishing.

A Book-Length Report

Format technical and research reports as you would format other book-length sources. If the organization that issued the report assigned it a number, include the number in parentheses after the title. (See also the guidelines provided for citing works produced by government agencies.)

Jameson, R., & Dewey, J. (2009). Preliminary findings from an evaluation of the president’s physical fitness program in Pleasantville school district. Pleasantville, WA: Pleasantville Board of Education.

A Book Authored by a Government Agency

Treat these as you would a book published by a nongovernment organization, but be aware that these works may have an identification number listed. If so, include it in parentheses after the publication year.

U.S. Census Bureau. (2002). The decennial censuses from 1790 to 2000 (Publication No. POL/02-MA). Washington, DC: US Government Printing Offices.

Revisit the references section you began to compile in Note 13.73 “Exercise 1” . Use the guidelines provided to format any entries for book-length print sources that you were unable to finish earlier.

Review how Jorge formatted these book-length print sources:

Atkins, R. C. (2002). Dr. Atkins’ diet revolution . New York, NY: M. Evans and Company.

Agatson, A. (2003). The South Beach diet. New York, NY: St. Martin’s Griffin.

Print Sources: Periodicals

An article in a scholarly journal.

Include the following information:

  • Author or authors’ names
  • Publication year
  • Article title (in sentence case, without quotation marks or italics)
  • Journal title (in title case and in italics)
  • Volume number (in italics)
  • Issue number (in parentheses)
  • Page number(s) where the article appears

DeMarco, R. F. (2010). Palliative care and African American women living with HIV. Journal of Nursing Education, 49 (5), 1–4.

An Article in a Journal Paginated by Volume

In these types of journals, page numbers for one volume continue across all the issues in that volume. For instance, the winter issue may begin with page 1, and in the spring issue that follows, the page numbers pick up where the previous issue left off. (If you have ever wondered why a print journal did not begin on page 1, or wondered why the page numbers of a journal extend into four digits, this is why.) Omit the issue number from your reference entry.

Wagner, J. (2009). Rethinking school lunches: A review of recent literature. American School Nurses’ Journal , 47, 1123–1127.

An Abstract of a Scholarly Article

At times you may need to cite an abstract—the summary that appears at the beginning—of a published article. If you are citing the abstract only, and it was published separately from the article, provide the following information:

  • Publication information for the article
  • Information about where the abstract was published (for instance, another journal or a collection of abstracts)

When creating a references section, use this format for abstracts published in a collection of abstracts

A Journal Article with Two to Seven Authors

List all the authors’ names in the order they appear in the article. Use an ampersand before the last name listed.

Barker, E. T., & Bornstein, M. H. (2010). Global self-esteem, appearance satisfaction, and self-reported dieting in early adolescence. Journal of Early Adolescence, 30 (2), 205–224.

Tremblay, M. S., Shields, M., Laviolette, M., Craig, C. L., Janssen, I., & Gorber, S. C. (2010). Fitness of Canadian children and youth: Results from the 2007–2009 Canadian Health Measures Survey. Health Reports, 21 (1), 7–20.

A Journal Article with More Than Seven Authors

List the first six authors’ names, followed by a comma, an ellipsis, and the name of the last author listed. The article in the following example has sixteen listed authors; the reference entry lists the first six authors and the sixteenth, omitting the seventh through the fifteenth.

When creating a references section, because some names are omitted, use a comma and an ellipsis, rather than an ampersand, before the final name listed

Writing at Work

The idea of an eight-page article with sixteen authors may seem strange to you—especially if you are in the midst of writing a ten-page research paper on your own. More often than not, articles in scholarly journals list multiple authors. Sometimes, the authors actually did collaborate on writing and editing the published article. In other instances, some of the authors listed may have contributed to the research in some way while being only minimally involved in the process of writing the article. Whenever you collaborate with colleagues to produce a written product, follow your profession’s conventions for giving everyone proper credit for their contribution.

A Magazine Article

After the publication year, list the issue date. Otherwise, treat these as you would journal articles. List the volume and issue number if both are available.

When creating a references section, oist the month after the year. For weekly magazines, list the full date, e.g.

A Newspaper Article

Treat these as you would magazine and journal articles, with one important difference: precede the page number(s) with the abbreviation p. (for a single-page article) or pp. (for a multipage article). For articles whose pagination is not continuous, list all the pages included in the article. For example, an article that begins on page A1 and continues on pages A4 would have the page reference A1, A4. An article that begins on page A1 and continues on pages A4 and A5 would have the page reference A1, A4–A5.

When creating a references section, include the section in your page reference.

A Letter to the Editor

After the title, indicate in brackets that the work is a letter to the editor.

Jones, J. (2009, January 31). Food police in our schools [Letter to the editor]. Rockwood Gazette, p. A8.

After the title, indicate in brackets that the work is a review and state the name of the work being reviewed. (Note that even if the title of the review is the same as the title of the book being reviewed, as in the following example, you should treat it as an article title. Do not italicize it.)

When creating a references section, italicize the title of the reviewed book only where it appears in brackets

Revisit the references section you began to compile in Note 13.73 “Exercise 1” . Use the guidelines provided above to format any entries for periodicals and other shorter print sources that you were unable to finish earlier.

Electronic Sources

Citing articles from online periodicals: urls and digital object identifiers (dois).

Whenever you cite online sources, it is important to provide the most up-to-date information available to help readers locate the source. In some cases, this means providing an article’s URL , or web address. (The letters URL stand for uniform resource locator.) Always provide the most complete URL possible. Provide a link to the specific article used, rather than a link to the publication’s homepage.

As you know, web addresses are not always stable. If a website is updated or reorganized, the article you accessed in April may move to a different location in May. The URL you provided may become a dead link. For this reason, many online periodicals, especially scholarly publications, now rely on DOIs rather than URLs to keep track of articles.

A DOI is a Digital Object Identifier—an identification code provided for some online documents, typically articles in scholarly journals. Like a URL, its purpose is to help readers locate an article. However, a DOI is more stable than a URL, so it makes sense to include it in your reference entry when possible. Follow these guidelines:

  • If you are citing an online article with a DOI, list the DOI at the end of the reference entry.
  • If the article appears in print as well as online, you do not need to provide the URL. However, include the words Electronic version after the title in brackets.
  • In other respects, treat the article as you would a print article. Include the volume number and issue number if available. (Note, however, that these may not be available for some online periodicals).

An Article from an Online Periodical with a DOI

List the DOI if one is provided. There is no need to include the URL if you have listed the DOI.

Bell, J. R. (2006). Low-carb beats low-fat diet for early losses but not long term. OBGYN News, 41 (12), 32. doi:10.1016/S0029-7437(06)71905-X

An Article from an Online Periodical with No DOI

List the URL. Include the volume and issue number for the periodical if this information is available. (For some online periodicals, it may not be.)

When creating a references section, use the words

Note that if the article appears in a print version of the publication, you do not need to list the URL, but do indicate that you accessed the electronic version.

Robbins, K. (2010, March/April). Nature’s bounty: A heady feast [Electronic version]. Psychology Today, 43 (2), 58.

Provide the URL of the article.

McNeil, D. G. (2010, May 3). Maternal health: A new study challenges benefits of vitamin A for women and babies. The New York Times. Retrieved from http://www.nytimes.com/2010/05/04/health/04glob.html?ref=health

An Article Accessed through a Database

Cite these articles as you would normally cite a print article. Provide database information only if the article is difficult to locate.

APA style does not require writers to provide the item number or accession number for articles retrieved from databases. You may choose to do so if the article is difficult to locate or the database is an obscure one. Check with your professor to see if this is something he or she would like you to include.

An Abstract of an Article

Format these as you would an article citation, but add the word Abstract in brackets after the title.

Bradley, U., Spence, M., Courtney, C. H., McKinley, M. C., Ennis, C. N., McCance, D. R.…Hunter, S. J. (2009). Low-fat versus low-carbohydrate weight reduction diets: Effects on weight loss, insulin resistance, and cardiovascular risk: A randomized control trial [Abstract]. Diabetes , 58 (12), 2741–2748. http://diabetes.diabetesjournals.org/content/early/2009/08/23/db00098.abstract

A Nonperiodical Web Document

The ways you cite different nonperiodical web documents may vary slightly from source to source, depending on the information that is available. In your citation, include as much of the following information as you can:

  • Name of the author(s), whether an individual or organization
  • Date of publication (Use n.d. if no date is available.)
  • Title of the document
  • Address where you retrieved the document

If the document consists of more than one web page within the site, link to the homepage or the entry page for the document.

American Heart Association. (2010). Heart attack, stroke, and cardiac arrest warning signs. Retrieved from http://www.americanheart.org/presenter.jhtml?identifier=3053

An Entry from an Online Encyclopedia or Dictionary

Because these sources often do not include authors’ names, you may list the title of the entry at the beginning of the citation. Provide the URL for the specific entry.

Addiction. (n.d.) In Merriam-Webster’s online dictionary . Retrieved from http://www.merriam-webster.com/dictionary/addiction

If you cite raw data compiled by an organization, such as statistical data, provide the URL where you retrieved the information. Provide the name of the organization that sponsors the site.

US Food and Drug Administration. (2009). Nationwide evaluation of X-ray trends: NEXT surveys performed [Data file]. Retrieved from http://www.fda.gov/Radiation-EmittingProducts/RadiationSafety/NationwideEvaluationofX- RayTrendsNEXT/ucm116508.htm

Graphic Data

When citing graphic data—such as maps, pie charts, bar graphs, and so on—include the name of the organization that compiled the information, along with the publication date. Briefly describe the contents in brackets. Provide the URL where you retrieved the information. (If the graphic is associated with a specific project or document, list it after your bracketed description of the contents.)

US Food and Drug Administration. (2009). [Pie charts showing the percentage breakdown of the FDA’s budget for fiscal year 2005]. 2005 FDA budget summary . Retrieved from mhttp://www.fda.gov/AboutFDA/ReportsManualsForms/Reports/BudgetReports/2005FDABudgetSummary/ucm117231.htm

An Online Interview (Audio File or Transcript)

List the interviewer, interviewee, and date. After the title, include bracketed text describing the interview as an “Interview transcript” or “Interview audio file,” depending on the format of the interview you accessed. List the name of the website and the URL where you retrieved the information. Use the following format.

Davies, D. (Interviewer), & Pollan, M. (Interviewee). (2008). Michael Pollan offers president food for thought [Interview transcript]. Retrieved from National Public Radio website: http://www.npr.org/templates/transcript/transcript.php?storyId=100755362

An Electronic Book

Electronic books may include books available as text files online or audiobooks. If an electronic book is easily available in print, cite it as you would a print source. If it is unavailable in print (or extremely difficult to find), use the format in the example. (Use the words Available from in your citation if the book must be purchased or is not available directly.)

Chisholm, L. (n.d.). Celtic tales. Retrieved from http://www.childrenslibrary.org/icdl/BookReader?bookid= chicelt_00150014&twoPage=false&route=text&size=0&fullscreen=false&pnum1=1&lang= English&ilang=English

A Chapter from an Online Book or a Chapter or Section of a Web Document

These are treated similarly to their print counterparts with the addition of retrieval information. Include the chapter or section number in parentheses after the book title.

Hart, A. M. (1895). Restoratives—Coffee, cocoa, chocolate. In Diet in sickness and in health (VI). Retrieved from http://www.archive.org/details/dietinsicknessin00hartrich

A Dissertation or Thesis from a Database

Provide the author, date of publication, title, and retrieval information. If the work is numbered within the database, include the number in parentheses at the end of the citation.

When creating a references section, italicize the titles of theses and dissertations.

Computer Software

For commonly used office software and programming languages, it is not necessary to provide a citation. Cite software only when you are using a specialized program, such as the nutrition tracking software in the following example. If you download software from a website, provide the version and the year if available.

Internet Brands, Inc. (2009). FitDay PC (Version 2) [Software]. Available from http://www.fitday.com/Pc/PcHome.html?gcid=14

A Post on a Blog or Video Blog

Citation guidelines for these sources are similar to those used for discussion forum postings. Briefly describe the type of source in brackets after the title.

When creating a references section, do not italicize the titles of blog or video blog postings

Because the content may not be carefully reviewed for accuracy, discussion forums and blogs should not be relied upon as a major source of information. However, it may be appropriate to cite these sources for some types of research. You may also participate in discussion forums or comment on blogs that address topics of personal or professional interest. Always keep in mind that when you post, you are making your thoughts public—and in many cases, available through search engines. Make sure any posts that can easily be associated with your name are appropriately professional, because a potential employer could view them.

A Television or Radio Broadcast

Include the name of the producer or executive producer; the date, title, and type of broadcast; and the associated company and location.

West, Ty. (Executive producer). (2009, September 24). PBS special report: Health care reform [Television broadcast]. New York, NY, and Washington, DC: Public Broadcasting Service.

A Television or Radio Series or Episode

Include the producer and the type of series if you are citing an entire television or radio series.

Couture, D., Nabors, S., Pinkard, S., Robertson, N., & Smith, J. (Producers). (1979). The Diane Rehm show [Radio series]. Washington, DC: National Public Radio.

To cite a specific episode of a radio or television series, list the name of the writer or writers (if available), the date the episode aired, its title, and the type of series, along with general information about the series.

Bernanke, J., & Wade, C. (2010, January 10). Hummingbirds: Magic in the air [Television series episode]. In F. Kaufman (Executive producer), Nature. New York, NY: WNET.

A Motion Picture

Name the director or producer (or both), year of release, title, country of origin, and studio.

Spurlock, M. (Director/producer), Morley, J. (Executive producer), & Winters. H. M. (Executive producer). (2004). Super size me. United States: Kathbur Pictures in association with Studio on Hudson.

A Recording

Name the primary contributors and list their role. Include the recording medium in brackets after the title. Then list the location and the label.

Smith, L. W. (Speaker). (1999). Meditation and relaxation [CD]. New York, NY: Earth, Wind, & Sky Productions.

Székely, I. (Pianist), Budapest Symphony Orchestra (Performers), & Németh, G. (Conductor). (1988). Chopin piano concertos no. 1 and 2 [CD]. Hong Kong: Naxos.

Provide as much information as possible about the writer, director, and producer; the date the podcast aired; its title; any organization or series with which it is associated; and where you retrieved the podcast.

Kelsey, A. R. (Writer), Garcia, J. (Director), & Kim, S. C. (Producer). (2010, May 7). Lies food labels tell us. Savvy consumer podcasts [Audio podcast] . Retrieved from http://www.savvyconsumer.org/podcasts/050710

Revisit the references section you began to compile in Note 13.73 “Exercise 1” .

  • Use the APA guidelines provided in this section to format any entries for electronic sources that you were unable to finish earlier.
  • If your sources include a form of media not covered in the APA guidelines here, consult with a writing tutor or review a print or online reference book. You may wish to visit the website of the American Psychological Association at http://www.apa.org or the Purdue University Online Writing lab at http://owl.english.purdue.edu , which regularly updates its online style guidelines.
  • Give your paper a final edit to check the references section.

Key Takeaways

In APA papers, entries in the references section include as much of the following information as possible:

  • Print sources. Author(s), date of publication, title, publisher, page numbers (for shorter works), editors (if applicable), and periodical title (if applicable).
  • Online sources (text-based). Author(s), date of publication, title, publisher or sponsoring organization, and DOI or URL (if applicable).
  • Electronic sources (non-text-based). Provide details about the creator(s) of the work, title, associated company or series, and date the work was produced or broadcast. The specific details provided will vary depending on the medium and the information that is available.
  • Electronic sources (text-based). If an electronic source is also widely available in print form, it is sometimes unnecessary to provide details about how to access the electronic version. Check the guidelines for the specific source type.

Writing for Success Copyright © 2015 by University of Minnesota is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

Purdue Online Writing Lab Purdue OWL® College of Liberal Arts

Reference List: Basic Rules

OWL logo

Welcome to the Purdue OWL

This page is brought to you by the OWL at Purdue University. When printing this page, you must include the entire legal notice.

Copyright ©1995-2018 by The Writing Lab & The OWL at Purdue and Purdue University. All rights reserved. This material may not be published, reproduced, broadcast, rewritten, or redistributed without permission. Use of this site constitutes acceptance of our terms and conditions of fair use.

This resourse, revised according to the 7 th  edition APA Publication Manual, offers basic guidelines for formatting the reference list at the end of a standard APA research paper. Most sources follow fairly straightforward rules. However, because sources obtained from academic journals  carry special weight in research writing, these sources are subject to special rules . Thus, this page presents basic guidelines for citing academic journals separate from its "ordinary" basic guidelines. This distinction is made clear below.

Note:  Because the information on this page pertains to virtually all citations, we've highlighted one important difference between APA 6 and APA 7 with an underlined note written in red.  For more information, please consult the   Publication Manual of the American Psychological Association , (7 th  ed.).

Formatting a Reference List

Your reference list should appear at the end of your paper. It provides the information necessary for a reader to locate and retrieve any source you cite in the body of the paper. Each source you cite in the paper must appear in your reference list; likewise, each entry in the reference list must be cited in your text.

Your references should begin on a new page separate from the text of the essay; label this page "References" in bold, centered at the top of the page (do NOT underline or use quotation marks for the title). All text should be double-spaced just like the rest of your essay.

Basic Rules for Most Sources

  • All lines after the first line of each entry in your reference list should be indented one-half inch from the left margin. This is called hanging indentation.
  • All authors' names should be inverted (i.e., last names should be provided first).
  • For example, the reference entry for a source written by Jane Marie Smith would begin with "Smith, J. M."
  • If a middle name isn't available, just initialize the author's first name: "Smith, J."
  • Give the last name and first/middle initials for all authors of a particular work up to and including 20 authors ( this is a new rule, as APA 6 only required the first six authors ). Separate each author’s initials from the next author in the list with a comma. Use an ampersand (&) before the last author’s name. If there are 21 or more authors, use an ellipsis (but no ampersand) after the 19th author, and then add the final author’s name.
  • Reference list entries should be alphabetized by the last name of the first author of each work.
  • For multiple articles by the same author, or authors listed in the same order, list the entries in chronological order, from earliest to most recent.
  • Note again that the titles of academic journals are subject to special rules. See section below.
  • Italicize titles of longer works (e.g., books, edited collections, names of newspapers, and so on).
  • Do not italicize, underline, or put quotes around the titles of shorter works such as chapters in books or essays in edited collections.

Basic Rules for Articles in Academic Journals

  • Present journal titles in full.
  • Italicize journal titles.
  • For example, you should use  PhiloSOPHIA  instead of  Philosophia,  or  Past & Present   instead of  Past and Present.
  • This distinction is based on the type of source being cited. Academic journal titles have all major words capitalized, while other sources' titles do not.
  • Capitalize   the first word of the titles and subtitles of   journal articles , as well as the   first word after a colon or a dash in the title, and   any proper nouns .
  • Do not italicize or underline the article title.
  • Deep blue: The mysteries of the Marianas Trench.
  • Oceanographic Study: A Peer-Reviewed Publication

Please note:  While the APA manual provides examples of how to cite common types of sources, it does not cover all conceivable sources. If you must cite a source that APA does not address, the APA suggests finding an example that is similar to your source and using that format. For more information, see page 282 of the   Publication Manual of the American Psychological Association , 7 th  ed.

Have a language expert improve your writing

Run a free plagiarism check in 10 minutes, automatically generate references for free.

  • Knowledge Base
  • Referencing

A Quick Guide to Harvard Referencing | Citation Examples

Published on 14 February 2020 by Jack Caulfield . Revised on 15 September 2023.

Referencing is an important part of academic writing. It tells your readers what sources you’ve used and how to find them.

Harvard is the most common referencing style used in UK universities. In Harvard style, the author and year are cited in-text, and full details of the source are given in a reference list .

Harvard Reference Generator

Instantly correct all language mistakes in your text

Be assured that you'll submit flawless writing. Upload your document to correct all your mistakes.

upload-your-document-ai-proofreader

Table of contents

Harvard in-text citation, creating a harvard reference list, harvard referencing examples, referencing sources with no author or date, frequently asked questions about harvard referencing.

A Harvard in-text citation appears in brackets beside any quotation or paraphrase of a source. It gives the last name of the author(s) and the year of publication, as well as a page number or range locating the passage referenced, if applicable:

Note that ‘p.’ is used for a single page, ‘pp.’ for multiple pages (e.g. ‘pp. 1–5’).

An in-text citation usually appears immediately after the quotation or paraphrase in question. It may also appear at the end of the relevant sentence, as long as it’s clear what it refers to.

When your sentence already mentions the name of the author, it should not be repeated in the citation:

Sources with multiple authors

When you cite a source with up to three authors, cite all authors’ names. For four or more authors, list only the first name, followed by ‘ et al. ’:

Sources with no page numbers

Some sources, such as websites , often don’t have page numbers. If the source is a short text, you can simply leave out the page number. With longer sources, you can use an alternate locator such as a subheading or paragraph number if you need to specify where to find the quote:

Multiple citations at the same point

When you need multiple citations to appear at the same point in your text – for example, when you refer to several sources with one phrase – you can present them in the same set of brackets, separated by semicolons. List them in order of publication date:

Multiple sources with the same author and date

If you cite multiple sources by the same author which were published in the same year, it’s important to distinguish between them in your citations. To do this, insert an ‘a’ after the year in the first one you reference, a ‘b’ in the second, and so on:

The only proofreading tool specialized in correcting academic writing

The academic proofreading tool has been trained on 1000s of academic texts and by native English editors. Making it the most accurate and reliable proofreading tool for students.

how write reference research paper

Correct my document today

A bibliography or reference list appears at the end of your text. It lists all your sources in alphabetical order by the author’s last name, giving complete information so that the reader can look them up if necessary.

The reference entry starts with the author’s last name followed by initial(s). Only the first word of the title is capitalised (as well as any proper nouns).

Harvard reference list example

Sources with multiple authors in the reference list

As with in-text citations, up to three authors should be listed; when there are four or more, list only the first author followed by ‘ et al. ’:

Reference list entries vary according to source type, since different information is relevant for different sources. Formats and examples for the most commonly used source types are given below.

  • Entire book
  • Book chapter
  • Translated book
  • Edition of a book

Journal articles

  • Print journal
  • Online-only journal with DOI
  • Online-only journal with no DOI
  • General web page
  • Online article or blog
  • Social media post

Sometimes you won’t have all the information you need for a reference. This section covers what to do when a source lacks a publication date or named author.

No publication date

When a source doesn’t have a clear publication date – for example, a constantly updated reference source like Wikipedia or an obscure historical document which can’t be accurately dated – you can replace it with the words ‘no date’:

Note that when you do this with an online source, you should still include an access date, as in the example.

When a source lacks a clearly identified author, there’s often an appropriate corporate source – the organisation responsible for the source – whom you can credit as author instead, as in the Google and Wikipedia examples above.

When that’s not the case, you can just replace it with the title of the source in both the in-text citation and the reference list:

Harvard referencing uses an author–date system. Sources are cited by the author’s last name and the publication year in brackets. Each Harvard in-text citation corresponds to an entry in the alphabetised reference list at the end of the paper.

Vancouver referencing uses a numerical system. Sources are cited by a number in parentheses or superscript. Each number corresponds to a full reference at the end of the paper.

A Harvard in-text citation should appear in brackets every time you quote, paraphrase, or refer to information from a source.

The citation can appear immediately after the quotation or paraphrase, or at the end of the sentence. If you’re quoting, place the citation outside of the quotation marks but before any other punctuation like a comma or full stop.

In Harvard referencing, up to three author names are included in an in-text citation or reference list entry. When there are four or more authors, include only the first, followed by ‘ et al. ’

Though the terms are sometimes used interchangeably, there is a difference in meaning:

  • A reference list only includes sources cited in the text – every entry corresponds to an in-text citation .
  • A bibliography also includes other sources which were consulted during the research but not cited.

Cite this Scribbr article

If you want to cite this source, you can copy and paste the citation or click the ‘Cite this Scribbr article’ button to automatically add the citation to our free Reference Generator.

Caulfield, J. (2023, September 15). A Quick Guide to Harvard Referencing | Citation Examples. Scribbr. Retrieved 12 February 2024, from https://www.scribbr.co.uk/referencing/harvard-style/

Is this article helpful?

Jack Caulfield

Jack Caulfield

Other students also liked, harvard in-text citation | a complete guide & examples, harvard style bibliography | format & examples, referencing books in harvard style | templates & examples, scribbr apa citation checker.

An innovative new tool that checks your APA citations with AI software. Say goodbye to inaccurate citations!

how write reference research paper

Writing Center Home Page

OASIS: Writing Center

Reference list: common reference list examples, article (with doi).

Alvarez, E., & Tippins, S. (2019). Socialization agents that Puerto Rican college students use to make financial decisions. Journal of Social Change , 11 (1), 75–85. https://doi.org/10.5590/JOSC.2019.11.1.07

Laplante, J. P., & Nolin, C. (2014). Consultas and socially responsible investing in Guatemala: A case study examining Maya perspectives on the Indigenous right to free, prior, and informed consent. Society & Natural Resources , 27 , 231–248. https://doi.org/10.1080/08941920.2013.861554

Use the DOI number for the source whenever one is available. DOI stands for "digital object identifier," a number specific to the article that can help others locate the source. In APA 7, format the DOI as a web address. Active hyperlinks for DOIs and URLs should be used for documents meant for screen reading. Present these hyperlinks in blue and underlined text (the default formatting in Microsoft Word), although plain black text is also acceptable. Be consistent in your formatting choice for DOIs and URLs throughout your reference list. Also see our Quick Answer FAQ, "Can I use the DOI format provided by library databases?"

Jerrentrup, A., Mueller, T., Glowalla, U., Herder, M., Henrichs, N., Neubauer, A., & Schaefer, J. R. (2018). Teaching medicine with the help of “Dr. House.” PLoS ONE , 13 (3), Article e0193972. https://doi.org/10.1371/journal.pone.0193972

For journal articles that are assigned article numbers rather than page ranges, include the article number in place of the page range.
For more on citing electronic resources, see  Electronic Sources References .

YouTube

Article (Without DOI)

Found in a common academic research database or in print.

Casler , T. (2020). Improving the graduate nursing experience through support on a social media platform. MEDSURG Nursing , 29 (2), 83–87.

If an article does not have a DOI and you retrieved it from a common academic research database through the university library, there is no need to include any additional electronic retrieval information. The reference list entry looks like the entry for a print copy of the article. (This format differs from APA 6 guidelines that recommended including the URL of a journal's homepage when the DOI was not available.) Note that APA 7 has additional guidance on reference list entries for articles found only in specific databases or archives such as Cochrane Database of Systematic Reviews, UpToDate, ProQuest Dissertations and Theses Global, and university archives. See APA 7, Section 9.30 for more information.

Found on an Open Access Website

Eaton, T. V., & Akers, M. D. (2007). Whistleblowing and good governance. CPA Journal , 77 (6), 66–71. http://archives.cpajournal.com/2007/607/essentials/p58.htm

Provide the direct web address/URL to a journal article found on the open web, often on an open access journal's website. In APA 7, active hyperlinks for DOIs and URLs should be used for documents meant for screen reading. Present these hyperlinks in blue and underlined text (the default formatting in Microsoft Word), although plain black text is also acceptable. Be consistent in your formatting choice for DOIs and URLs throughout your reference list.

Weinstein, J. A. (2010).  Social change  (3rd ed.). Rowman & Littlefield.

If the book has an edition number, include it in parentheses after the title of the book. If the book does not list any edition information, do not include an edition number. The edition number is not italicized.

American Nurses Association. (2015). Nursing: Scope and standards of practice (3rd ed.).

If the author and publisher are the same, only include the author in its regular place and omit the publisher.

Lencioni, P. (2012). The advantage: Why organizational health trumps everything else in business . Jossey-Bass. https://amzn.to/343XPSJ

As a change from APA 6 to APA 7, it is no longer necessary to include the ebook format in the title. However, if you listened to an audiobook and the content differs from the text version (e.g., abridged content) or your discussion highlights elements of the audiobook (e.g., narrator's performance), then note that it is an audiobook in the title element in brackets. For ebooks and online audiobooks, also include the DOI number (if available) or nondatabase URL but leave out the electronic retrieval element if the ebook was found in a common academic research database, as with journal articles. APA 7 allows for the shortening of long DOIs and URLs, as shown in this example. See APA 7, Section 9.36 for more information.

Chapter in an Edited Book

Poe, M. (2017). Reframing race in teaching writing across the curriculum. In F. Condon & V. A. Young (Eds.), Performing antiracist pedagogy in rhetoric, writing, and communication (pp. 87–105). University Press of Colorado.

Include the page numbers of the chapter in parentheses after the book title.

Christensen, L. (2001). For my people: Celebrating community through poetry. In B. Bigelow, B. Harvey, S. Karp, & L. Miller (Eds.), Rethinking our classrooms: Teaching for equity and justice (Vol. 2, pp. 16–17). Rethinking Schools.

Also include the volume number or edition number in the parenthetical information after the book title when relevant.

Freud, S. (1961). The ego and the id. In J. Strachey (Ed.),  The standard edition of the complete psychological works of Sigmund Freud  (Vol. 19, pp. 3-66). Hogarth Press. (Original work published 1923)

When a text has been republished as part of an anthology collection, after the author’s name include the date of the version that was read. At the end of the entry, place the date of the original publication inside parenthesis along with the note “original work published.” For in-text citations of republished work, use both dates in the parenthetical citation, original date first with a slash separating the years, as in this example: Freud (1923/1961). For more information on reprinted or republished works, see APA 7, Sections 9.40-9.41.

Classroom Resources

Citing classroom resources.

If you need to cite content found in your online classroom, use the author (if there is one listed), the year of publication (if available), the title of the document, and the main URL of Walden classrooms. For example, you are citing study notes titled "Health Effects of Exposure to Forest Fires," but you do not know the author's name, your reference entry will look like this:

Health effects of exposure to forest fires [Lecture notes]. (2005). Walden University Canvas. https://waldenu.instructure.com

If you do know the author of the document, your reference will look like this:

Smith, A. (2005). Health effects of exposure to forest fires [PowerPoint slides]. Walden University Canvas. https://waldenu.instructure.com  

A few notes on citing course materials:

  • [Lecture notes]
  • [Course handout]
  • [Study notes]
  • It can be difficult to determine authorship of classroom documents. If an author is listed on the document, use that. If the resource is clearly a product of Walden (such as the course-based videos), use Walden University as the author. If you are unsure or if no author is indicated, place the title in the author spot, as above.
  • If you cannot determine a date of publication, you can use n.d. (for "no date") in place of the year.

Note:  The web location for Walden course materials is not directly retrievable without a password, and therefore, following APA guidelines, use the main URL for the class sites: https://class.waldenu.edu.

Citing Tempo Classroom Resources

Clear author: 

Smith, A. (2005). Health effects of exposure to forest fires [PowerPoint slides]. Walden University Brightspace. https://mytempo.waldenu.edu

Unclear author:

Health effects of exposure to forest fires [Lecture notes]. (2005). Walden University Brightspace. https://mytempo.waldenu.edu

Conference Sessions and Presentations

Feinman, Y. (2018, July 27). Alternative to proctoring in introductory statistics community college courses [Poster presentation]. Walden University Research Symposium, Minneapolis, MN, United States. https://scholarworks.waldenu.edu/symposium2018/23/

Torgerson, K., Parrill, J., & Haas, A. (2019, April 5-9). Tutoring strategies for online students [Conference session]. The Higher Learning Commission Annual Conference, Chicago, IL, United States. http://onlinewritingcenters.org/scholarship/torgerson-parrill-haas-2019/

Dictionary Entry

Merriam-Webster. (n.d.). Leadership. In Merriam-Webster.com dictionary . Retrieved May 28, 2020, from https://www.merriam-webster.com/dictionary/leadership

When constructing a reference for an entry in a dictionary or other reference work that has no byline (i.e., no named individual authors), use the name of the group—the institution, company, or organization—as author (e.g., Merriam Webster, American Psychological Association, etc.). The name of the entry goes in the title position, followed by "In" and the italicized name of the reference work (e.g., Merriam-Webster.com dictionary , APA dictionary of psychology ). In this instance, APA 7 recommends including a retrieval date as well for this online source since the contents of the page change over time. End the reference entry with the specific URL for the defined word.

Discussion Board Post

Osborne, C. S. (2010, June 29). Re: Environmental responsibility [Discussion post]. Walden University Canvas.  https://waldenu.instructure.com  

Dissertations or Theses

Retrieved From a Database

Nalumango, K. (2019). Perceptions about the asylum-seeking process in the United States after 9/11 (Publication No. 13879844) [Doctoral dissertation, Walden University]. ProQuest Dissertations and Theses.

Retrieved From an Institutional or Personal Website

Evener. J. (2018). Organizational learning in libraries at for-profit colleges and universities [Doctoral dissertation, Walden University]. ScholarWorks. https://scholarworks.waldenu.edu/cgi/viewcontent.cgi?article=6606&context=dissertations

Unpublished Dissertation or Thesis

Kirwan, J. G. (2005). An experimental study of the effects of small-group, face-to-face facilitated dialogues on the development of self-actualization levels: A movement towards fully functional persons [Unpublished doctoral dissertation]. Saybrook Graduate School and Research Center.

For further examples and information, see APA 7, Section 10.6.

Legal Material

For legal references, APA follows the recommendations of The Bluebook: A Uniform System of Citation , so if you have any questions beyond the examples provided in APA, seek out that resource as well.

Court Decisions

Reference format:

Name v. Name, Volume Reporter Page (Court Date). URL

Sample reference entry:

Brown v. Board of Education, 347 U.S. 483 (1954). https://www.oyez.org/cases/1940-1955/347us483

Sample citation:

In Brown v. Board of Education (1954), the Supreme Court ruled racial segregation in schools unconstitutional.

Note: Italicize the case name when it appears in the text of your paper.

Name of Act, Title Source § Section Number (Year). URL

Sample reference entry for a federal statute:

Individuals With Disabilities Education Act, 20 U.S.C. § 1400 et seq. (2004). https://www.congress.gov/108/plaws/publ446/PLAW-108publ446.pdf

Sample reference entry for a state statute:

Minnesota Nurse Practice Act, Minn. Stat. §§ 148.171 et seq. (2019). https://www.revisor.mn.gov/statutes/cite/148.171

Sample citation: Minnesota nurses must maintain current registration in order to practice (Minnesota Nurse Practice Act, 2010).

Note: The § symbol stands for "section." Use §§ for sections (plural). To find this symbol in Microsoft Word, go to "Insert" and click on Symbol." Look in the Latin 1-Supplement subset. Note: U.S.C. stands for "United States Code." Note: The Latin abbreviation " et seq. " means "and what follows" and is used when the act includes the cited section and ones that follow. Note: List the chapter first followed by the section or range of sections.

Unenacted Bills and Resolutions

(Those that did not pass and become law)

Title [if there is one], bill or resolution number, xxx Cong. (year). URL

Sample reference entry for Senate bill:

Anti-Phishing Act, S. 472, 109th Cong. (2005). https://www.congress.gov/bill/109th-congress/senate-bill/472

Sample reference entry for House of Representatives resolution:

Anti-Phishing Act, H.R. 1099, 109th Cong. (2005). https://www.congress.gov/bill/109th-congress/house-bill/1099

The Anti-Phishing Act (2005) proposed up to 5 years prison time for people running Internet scams.

These are the three legal areas you may be most apt to cite in your scholarly work. For more examples and explanation, see APA 7, Chapter 11.

Magazine Article

Clay, R. (2008, June). Science vs. ideology: Psychologists fight back about the misuse of research. Monitor on Psychology , 39 (6). https://www.apa.org/monitor/2008/06/ideology

Note that for citations, include only the year: Clay (2008). For magazine articles retrieved from a common academic research database, leave out the URL. For magazine articles from an online news website that is not an online version of a print magazine, follow the format for a webpage reference list entry.

Newspaper Article (Retrieved Online)

Baker, A. (2014, May 7). Connecticut students show gains in national tests. New York Times . http://www.nytimes.com/2014/05/08/nyregion/national-assessment-of-educational-progress-results-in-Connecticut-and-New-Jersey.html

Include the full date in the format Year, Month Day. Do not include a retrieval date for periodical sources found on websites. Note that for citations, include only the year: Baker (2014). For newspaper articles retrieved from a common academic research database, leave out the URL. For newspaper articles from an online news website that is not an online version of a print newspaper, follow the format for a webpage reference list entry.

Online Video/Webcast

Walden University. (2013).  An overview of learning  [Video]. Walden University Canvas.  https://waldenu.instructure.com  

Use this format for online videos such as Walden videos in classrooms. Most of our classroom videos are produced by Walden University, which will be listed as the author in your reference and citation. Note: Some examples of audiovisual materials in the APA manual show the word “Producer” in parentheses after the producer/author area. In consultation with the editors of the APA manual, we have determined that parenthetical is not necessary for the videos in our courses. The manual itself is unclear on the matter, however, so either approach should be accepted. Note that the speaker in the video does not appear in the reference list entry, but you may want to mention that person in your text. For instance, if you are viewing a video where Tobias Ball is the speaker, you might write the following: Tobias Ball stated that APA guidelines ensure a consistent presentation of information in student papers (Walden University, 2013). For more information on citing the speaker in a video, see our page on Common Citation Errors .

Taylor, R. [taylorphd07]. (2014, February 27). Scales of measurement [Video]. YouTube. https://www.youtube.com/watch?v=PDsMUlexaMY

Walden University Academic Skills Center. (2020, April 15). One-way ANCOVA: Introduction [Video]. YouTube. https://youtu.be/_XnNDQ5CNW8

For videos from streaming sites, use the person or organization who uploaded the video in the author space to ensure retrievability, whether or not that person is the speaker in the video. A username can be provided in square brackets. As a change from APA 6 to APA 7, include the publisher after the title, and do not use "Retrieved from" before the URL. See APA 7, Section 10.12 for more information and examples.

See also reference list entry formats for TED Talks .

Technical and Research Reports

Edwards, C. (2015). Lighting levels for isolated intersections: Leading to safety improvements (Report No. MnDOT 2015-05). Center for Transportation Studies. http://www.cts.umn.edu/Publications/ResearchReports/reportdetail.html?id=2402

Technical and research reports by governmental agencies and other research institutions usually follow a different publication process than scholarly, peer-reviewed journals. However, they present original research and are often useful for research papers. Sometimes, researchers refer to these types of reports as gray literature , and white papers are a type of this literature. See APA 7, Section 10.4 for more information.

Reference list entires for TED Talks follow the usual guidelines for multimedia content found online. There are two common places to find TED talks online, with slightly different reference list entry formats for each.

TED Talk on the TED website

If you find the TED Talk on the TED website, follow the format for an online video on an organizational website:

Owusu-Kesse, K. (2020, June). 5 needs that any COVID-19 response should meet [Video]. TED Conferences. https://www.ted.com/talks/kwame_owusu_kesse_5_needs_that_any_covid_19_response_should_meet

The speaker is the author in the reference list entry if the video is posted on the TED website. For citations, use the speaker's surname.

TED Talk on YouTube

If you find the TED Talk on YouTube or another streaming video website, follow the usual format for streaming video sites:

TED. (2021, February 5). The shadow pandemic of domestic violence during COVID-19 | Kemi DaSilvalbru [Video]. YouTube. https://www.youtube.com/watch?v=PGdID_ICFII

TED is the author in the reference list entry if the video is posted on YouTube since it is the channel on which the video is posted. For citations, use TED as the author.

Walden University Course Catalog

To include the Walden course catalog in your reference list, use this format:

Walden University. (2020). 2019-2020 Walden University catalog . https://catalog.waldenu.edu/index.php

If you cite from a specific portion of the catalog in your paper, indicate the appropriate section and paragraph number in your text:

...which reflects the commitment to social change expressed in Walden University's mission statement (Walden University, 2020, Vision, Mission, and Goals section, para. 2).

And in the reference list:

Walden University. (2020). Vision, mission, and goals. In 2019-2020 Walden University catalog. https://catalog.waldenu.edu/content.php?catoid=172&navoid=59420&hl=vision&returnto=search

Vartan, S. (2018, January 30). Why vacations matter for your health . CNN. https://www.cnn.com/travel/article/why-vacations-matter/index.html

For webpages on the open web, include the author, date, webpage title, organization/site name, and URL. (There is a slight variation for online versions of print newspapers or magazines. For those sources, follow the models in the previous sections of this page.)

American Federation of Teachers. (n.d.). Community schools . http://www.aft.org/issues/schoolreform/commschools/index.cfm

If there is no specified author, then use the organization’s name as the author. In such a case, there is no need to repeat the organization's name after the title.

In APA 7, active hyperlinks for DOIs and URLs should be used for documents meant for screen reading. Present these hyperlinks in blue and underlined text (the default formatting in Microsoft Word), although plain black text is also acceptable. Be consistent in your formatting choice for DOIs and URLs throughout your reference list.

Related Resources

Blogger

Knowledge Check: Common Reference List Examples

Didn't find what you need? Search our website or email us .

Read our website accessibility and accommodation statement .

  • Previous Page: Overview
  • Next Page: Common Military Reference List Examples
  • Office of Student Disability Services

Walden Resources

Departments.

  • Academic Residencies
  • Academic Skills
  • Career Planning and Development
  • Customer Care Team
  • Field Experience
  • Military Services
  • Student Success Advising
  • Writing Skills

Centers and Offices

  • Center for Social Change
  • Office of Academic Support and Instructional Services
  • Office of Degree Acceleration
  • Office of Research and Doctoral Services
  • Office of Student Affairs

Student Resources

  • Doctoral Writing Assessment
  • Form & Style Review
  • Quick Answers
  • ScholarWorks
  • SKIL Courses and Workshops
  • Walden Bookstore
  • Walden Catalog & Student Handbook
  • Student Safety/Title IX
  • Legal & Consumer Information
  • Website Terms and Conditions
  • Cookie Policy
  • Accessibility
  • Accreditation
  • State Authorization
  • Net Price Calculator
  • Contact Walden

Walden University is a member of Adtalem Global Education, Inc. www.adtalem.com Walden University is certified to operate by SCHEV © 2024 Walden University LLC. All rights reserved.

U.S. flag

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

  • Publications
  • Account settings
  • Advanced Search
  • Journal List
  • Indian J Orthop
  • v.53(3); May-Jun 2019

Logo of ijortho

Formatting References for Scientific Manuscripts

Srinivas b s kambhampati.

Sri Dhaatri Orthopaedic, Maternity and Gynaecology Center, Vijayawada, Andhra Pradesh, India

Lalit Maini

1 Department of Orthopaedics, Maulana Azad Medical College, New Delhi, India

While references are an essential and integral part of a scientific manuscript, format and style of references are as varied as the number of journals currently present. International Committee of Medical Journal Editors in their latest recommendations for publication, 1 advice authors to quote original references whenever possible. We would recommend the readers to go through these guidelines as they are given in sufficient detail to submit a good set of references including styling. Other resources for citing references include the PubMed section 2 which gives samples of formatting of different reference types and the eBook: Citing Medicine, 3 published by the U. S. National Library of Medicine, which gives assistance and rules to authors, editors, publishers and librarians for formatting of references for different reference types.

References are formatted in two basic styles – the Vancouver style which is numeric (more commonly used in medical journals) and Harvard which uses author-date style (more commonly used in natural and Social sciences journals). 4 Parts and order of the parts cited differ on what the author is citing (reference type) and the journal that is being submitted to. The most common types of references include journal article, book, book section or chapter, dissertation, monograph, and webpage. As an example, for a journal article, the parts of a reference in the sequence include authors, article title, journal title, date of publication, volume, issue, and location/pagination. Each journal has its own modification of the format for each part and the punctuation marks, or their lack of, between the parts. Formatting style in each part of a reference could involve placement of selected punctuation marks, bold and italics enhancements, alphabetical order or sequential ordering of references and style of citing in the text, making the combination of variations that create a unique reference style as large in number as the number of journals currently published. It is not clear why such a system has evolved, but it requires considerable attention to detail to get the formatting correct and is time-consuming for the author. The tradition of the journal has been thought as one of the reasons. 4 In manuscripts submitted for the Indian Journal of Orthopaedics (IJO), the reference section carries the most formatting errors committed by authors.

The advantage of having a constant style within a journal is two-fold, apart from an esthetic appearance of references across all articles published by the journal. Ease of reading the references at the end of each article and ease of finding reference part by the reader if he/she is used to the format and plans to look up the reference. As a student/professional in the medical field, one would require attention to finer details of his/her research work as well as in their clinical practice and hence exercising attention to the references would help improve those skills. Such a wide variation in the styles of references has also benefitted some software companies who deal with reference managers (RMs). Some RMs are free for use, and the authors are advised to use different RMs to see which one suits their needs best. While some RMs are cloud based, others are computer based and do not require an internet connection while some others are cloud and computer based. The variation in the style of references across journals appears unlikely to be standardized to a single universal format in the near future.

The Citation Style Language (CSL) is an XML-based computer language developed to standardize formatting of citations and references in manuscripts submitting to journals. They are text application editable files which are imported into RMs. An increasing number of RMs use CSL to help users format their list of references according to individual journal guidelines. However, not all journals are supported by CSL files.

There are two main repositories for access to CSL files – One by GitHub 5 and the other by Zotero 6 developed by Corporation for Digital Scholarship and Roy Rosenzweig Center for History and New Media. These contain more than 8500 styles of references. Authors using Zotero, Mendeley, RefWorks, Papers, CrossRef, Bibliography, and some 42 other RMs can use these CSL files to manage references within them. IJO did not have a CSL file until now in both the repositories. In this scenario, there are a few options for the authors preparing references for a manuscript. First, to type and style references manually which would take a long time and prone to human errors. Second, a CSL file similar to IJO may be selected from the repository and used and later manually edited, if any needed. However, this involves searching for an exact match of style for a journal registered in the repository of CSL files. Third, there are RMs with inbuilt options to format references while citing in the text. This option is independent of CSL. The disadvantage here is that the author is bound by the list of reference styles already loaded within the software. They may not be able to add new formats. Fourth, some RMs allow authors to prepare a style, but this would take some time to prepare if the style is not already inbuilt. As a fifth option, a CSL file that is close to IJO may be chosen, and the code of this file tweaked with minor editing to convert it for use with IJO. To do that, the author must be familiar with programming or editing of HTML/XML files since HTML is a language that is closer to XML.

Zotero's repository 7 website has a user-friendly interface in which such searches are easier to perform. It has 9357 styles stored in the repository at the time of writing this article on March 17, 2019. There are 1924 unique styles through which one can search if their required journal is listed. Zotero draws CSL files from GitHub into their repository. Hence, if a file is created in GitHub, it is drawn into Zotero by default. CSL Project 8 is a website sponsored by four well known RMs. These are Zotero, Mendeley, 9 Papers, 10 and RefWorks. 11 This website gives detailed specifications and documentation of CSL language if one is interested in coding these files. If one is proficient with XML, they can create a style and submit it to the GitHub website for others to benefit. Editing is easier if one uses the Zotero RM as it has an inbuilt option to edit style. It can be done even in other managers or with the use of a standard text editing application in Windows or Mac operating systems. Once a new CSL file is developed, in order to publish it, it has to be validated by CSL validator website 12 and submitted at the GitHub site for accepting into the repository. Even finer details like number of author names before et al. while formatting reference, punctuation marks and their placement, style of each part of the reference and each style of the reference, etc., can be edited accurately.

Once developed, the output of references and citations is remarkably consistent, and too much time need not be directed to editing the punctuation marks and styling of the references and citations while preparing the manuscript. The only hurdle after this would be to get full details of the references reliably and accurately into the RM database while importing the references. The author needs to check that the references were properly imported into the database. If verified, they may be used any number of times with precision. With appropriate selection, the citing as well as the list of references can be formatted according to the journal that is being considered, for submission. Those who are already using RMs may be well aware of the advantages and the time such CSL files can save while preparing a manuscript.

We are happy to inform that a CSL file for IJO has now been created in the GitHub repository 1 and Zotero Styles repository 3 and it can be used by authors using the RMs listed in the CSL website and benefit from its use. The direct link of the file in the repository is given 13 [ Figure 1 ]. Basic users of RMs may download it through their RMs by selecting Indian Journal of Orthopaedics option. Advanced users who know where to place this file may access using the weblink given. Examples of reference style and citation for IJO are given in Figure 2 .

An external file that holds a picture, illustration, etc.
Object name is IJOrtho-53-381-g001.jpg

Screenshot of browser shows the web address and search words used to retrieve Citation Style Language file for Indian Journal of Orthopaedics

An external file that holds a picture, illustration, etc.
Object name is IJOrtho-53-381-g002.jpg

Examples of format of references and their citation in text for the Indian Journal of Orthopaedics

How to Write References and Cite Sources in a Research Paper

Table of contents

  • 1.1 Academic Integrity
  • 1.2 Avoiding Plagiarism
  • 1.3 Building Credibility
  • 1.4 Facilitating Further Research
  • 2.1 APA (American Psychological Association)
  • 2.2 MLA (Modern Language Association)
  • 2.3 Chicago Style
  • 2.4 IEEE (Institute of Electrical and Electronics Engineers)
  • 3.1 Author(s)
  • 3.2 Title of the Source
  • 3.3 Publication Date
  • 3.4 Publisher
  • 3.5 Page Numbers
  • 3.6 DOI (Digital Object Identifier) or URL (Uniform Resource Locator)
  • 4.1.3 Chicago
  • 4.2.1 Citing Multiple Authors
  • 4.2.4 Chicago
  • 4.3 Page Numbers in In-Text Citations
  • 5.1 Formatting and Organizing Your References
  • 5.2 Alphabetizing Your References
  • 5.3.2 Journal
  • 5.3.3 Chapter
  • 5.3.4 Conference Paper/Presentation
  • 5.3.5 Online Sources
  • 6.1 Verify Your Source
  • 6.2 Follow the One Style Guide
  • 6.3 Verify DOI and URLs
  • 6.4 Online Citation Generators
  • 6.5 Use University Libraries and Writing Centers
  • 7 Leave No Stone Unturned!

Citation is necessary while writing your school essay, a publication, or a Master’s thesis. We all want our efforts to be acknowledged, right? The lack of references and citations can make the source think you are trying to steal their work. Hence, the question is how to go about making references.

Do you want to learn how to cite in a research paper? Then this article is for you, as it contains the details of how to reference when writing a research paper. There is a standard way to do this in educational journals and organizational publications.

Hence, a researcher must understand how to reference their writings or journals. It is another thing to write a journal properly, but crediting the sources is more crucial.

Follow this guide to learn:

  • The importance of referencing and citations for your academic works;
  • How to cite in APA, MLA, Chicago, IEEE, and ASA styles;
  • Essential guidelines to follow for a published work.

Why Referencing and Citation Matter

Another important question is: What is the need for referencing and citation? The major reason for citations in research paper format is to serve as directional cues for the employed knowledge. When you cite, readers can know that some portions of your content belong to you. Hence, it is easier to identify how recent the information is.

Citation for your paper comes with several advantages. They include:

Academic Integrity

The citation affirms the integrity of your academic writing. In this information age, there are several details, and it can be difficult to authenticate. When you reference, it helps readers understand the necessity of the discussed topic. Referencing certain authors can give more authority to your papers.

Avoiding Plagiarism

Plagiarism refers to the mindless lifting of details from another material without acknowledging the details. For the source, they could believe you are stealing from them. In most countries, copyright infringement is a punishable crime and can make you lose your hard work.

Building Credibility

Credibility is the goal of every academic scholar. There is no better way to gain relevance than by citing sources from other credible ones.

Facilitating Further Research

For other researchers like you, providing citations can serve as other sources for more information. It helps them to know other philosophies about the subject.

Choosing the Right Citation Style

Now that the advantages have been established, the new worry is the choice of the right style. There are several styles with their respective peculiarities. For example, the MLA writing style is common in liberal scientific paper citations. Let’s delve more into MLA formatting for research papers and other styles.

APA (American Psychological Association)

The commonest style used by many scholars is APA formatting , especially if there is no stated style. This approach employs the use of in-text citations to explain the source. It’s the simplest form of citation.

Here is an in-text referencing example:

“Exercise is a good way to recover from ailments.” APA, n.d. (American Psychological Association).

The reference style includes:

  • The author’s name;
  • The author’s name is in parenthesis to follow the referenced excerpt;
  • The publication date.

MLA (Modern Language Association)

MLA-style formation is concise and known for its scientific referencing format. The peculiarity of the MLA citation is its source citation, episode title, and document layout. You have to:

  • Include the parenthetical citation;
  • Create some spaces away from the left margin;
  • Include the author’s or source’s name.

Ensure you capitalize every word when including the names. You can employ professional MLA Citation Generators to make the compilation easier. It is perfect for the citation format of scientific papers.

Chicago Style

Chicago’s style is famous for two things:

  • The in-text citation within the paper;
  • The reference list is at its end.

It is an author-date approach. Hence, the in-text citation for a research paper has the author’s or source name and publication year.

IEEE (Institute of Electrical and Electronics Engineers)

This employs the use of numbers. It is chronological as it arranges the citation based on the order of appearance. A click on it takes the reader to the full reference at the end of the paper. To make it easier, you can employ IEEE Citation Maker for a well-curated task. This way, you won’t have to worry about the manual compilation of the IEEE citation style.

This is similar to the author-date approach by Chicago Style. You can:

  • Create the quotation;
  • Include the parentheses for the author’s name and publication date;
  • Add the page number using a colon.

Components of a Citation

Do you want to know how to complete a citation for your professional research paper writing service and research paper? Learn about its components.

The author is also regarded as the source. It is the original writer of the material you are referencing. Sometimes, there may be multiple authors. Do not miss out on anyone while citing a research paper.

Title of the Source

The title of the source is often the name given to the material by the author.

Publication Date

As the name implies, this refers to the date the source was published. Frequently, most writers include it at the start of their material. State the exact month and year of publication, separated with a comma. See example:

“(2016, March 7).”

Including the publisher’s details is only necessary for the full reference. It should be at the end of the paper. It can facilitate further research.

Page Numbers

The page number is necessary, as it helps to easily refer to different sections of the paper.

DOI (Digital Object Identifier) or URL (Uniform Resource Locator)

A DOI is a link to a resource on the internet. The resource can be a book or its chapter. On the other hand, a URL is an address that indicates where the resource can be found. It helps to locate the resource. The use of URLs and DOIs directs readers to the digital identifier of the source.

In-Text Citations

An in-text citation for a research paper is the brief form of the bibliography that you include in the body of the content. It contains the author’s family name and year of publication. It provides enough details to help users know the source in their reference list. Each citation format for research papers is unique.

See citation examples below.

How to Cite Direct Quotations for Each Citation Style

The general rule in referencing is that in-text citations must have a corresponding entry in your reference list. Let’s see how!

There are two types of APA in-text citations:

Parenthetical:

The researchers concluded, “Climate change poses significant challenges for coastal communities” (Johnson & Lee, 2021, p. 78).

In their study on the effects of exercise on mental health, Smith and Johnson (2019) found that regular physical activity was associated with a significant decrease in symptoms of anxiety and depression. According to their research, engaging in exercise three times a week for at least 30 minutes had a positive impact on participants’ overall well-being.

APA in-text citation style employs the source’s name and publication year. A direct quotation will include the page number. Remember, you can generate a citation in a research paper using the APA style via a citation generator.

MLA is known as the scientific style of citation. The uniqueness of MLA Style formatting is the use of a direct quote (in quotes), the Author’s name and page number (in parentheses).

In the novel “To Kill a Mockingbird,” Atticus Finch imparts wisdom to his children, saying, “You never really understand a person until you consider things from his point of view… until you climb into his skin and walk around in it” (Lee 30).

For Chicago, you are to include a parenthetical citation, the author’s name, the publication year, and the quote’s page number.

As Adams (2009) argues, “History is a vast early warning system” (53).

IEEE (Institute of Electrical and Electronics Engineers) style typically uses numerical citations in square brackets for in-text citations. It doesn’t rely heavily on direct quotations in the same way as some other citation styles, like APA or MLA. Instead, IEEE generally prefers paraphrasing and citing the source, but direct quotations can be used when necessary. Here’s an example of a direct quotation in IEEE style:

In-Text Citation:

As stated by Smith, “In most cases, the impedance of the transmission line remains relatively constant throughout its length” [1].

Corresponding Reference Entry:

[1] A. Smith, “Transmission Line Impedance Analysis,” IEEE Transactions on Electrical Engineering, vol. 45, no. 3, pp. 212-225, 2010.

ASA is different because it contains the author’s name, publication year, and even the page number.

According to Smith (2010), “Social institutions shape our behaviors and interactions in profound ways” (p. 45).

How to Cite Paraphrased Information

While writing a college paper, paraphrasing is important to achieve clarity, but it is ideal to cite the source of the paraphrased information. The proper way to cite paraphrased information is to include a parenthetical citation. The style of referencing for all citation styles doesn’t change, but they should be in parenthesis.

“Strength can be defined in terms of ability and acquired skills, according to (Jack et al. 2023).

Citing Multiple Authors

The technique is different when you are citing a source that has multiple authors. For the first-time citation, you should include the names of all the authors. The subsequent activities to generate a citation in APA should only include the first author’s surname and the proper use of ‘et al.’ However, you should include the surname and initials of all these authors in the full reference. Separate the authors with commas and ampersands before the final name.

Two Authors:

When a source has two authors, include both authors’ names in the in-text citation every time you reference the source. Use an ampersand (&) between the authors’ names, and include the year of publication in parentheses. For example:

(Smith & Johnson, 2020) found that…

Three to Five Authors:

When a source has three to five authors, list all authors in the first in-text citation. Use an ampersand (&) between the last two authors’ names. For subsequent citations of the same source, use only the first author’s name followed by “et al.” and the year. For example:

First citation: (Smith, Johnson, & Williams, 2018)…

Subsequent citations: (Smith et al., 2018)…

Six or More Authors:

When a source has six or more authors, you should use “et al.” in both the first and subsequent in-text citations, along with the year. For example:

(Smith et al., 2019) conducted a study on…

Group Authors:

When citing sources authored by a group, organization, or company, use the full name of the group or organization as the author in the in-text citation. If the abbreviation is well-known, you can use the abbreviation in subsequent citations. For example:

First citation: (American Psychological Association [APA], 2019)…

Subsequent citations: (APA, 2019)

When a source has two authors, include both authors’ names in the in-text citation, separated by the word “and.” For example:

(Smith and Johnson 45) found that…

Three or More Authors:

When a source has three or more authors, include only the first author’s name followed by “et al.” in the in-text citation. For example:

(Smith et al. 72) conducted a study on…

If a source has no identifiable author, use a shortened version of the title in the in-text citation. Enclose the title in double quotation marks or use italics if it’s a longer work (e.g., a book or film). For example:

(“Title of the Source” 28) argues that…

(American Psychological Association 62) states that…

Author-Date System:

In the Author-Date system, when a source has two authors, include both authors’ last names and the publication year in parentheses in the in-text citation, separated by an ampersand (&). For example:

(Smith & Johnson 2020) found that…

When a source has three or more authors, you can use “et al.” after the first author’s name in the in-text citation. For example:

(Smith et al. 2018) conducted a study on…

Notes and Bibliography System:

In the Notes and Bibliography system, when a source has two authors, include both authors’ full names in the note. For example:

John Smith and Jane Johnson, Title of the Work (Place of Publication: Publisher, Year), page number.

When a source has three or more authors, list the first author’s name followed by “et al.” in the note. For example:

John Smith et al., Title of the Work (Place of Publication: Publisher, Year), page number.

When a source has two authors, include both authors’ last names in the in-text citation, separated by the word “and.” For example:

(Smith and Johnson 2020) found that…

Three Authors:

When a source has three authors, include all three authors’ last names in the in-text citation, separated by commas. For example:

(Smith, Johnson, and Williams 2018) conducted a study on…

More than Three Authors:

When a source has more than three authors, you should use the first author’s last name followed by “et al.” in the in-text citation. For example:

(Smith et al. 2019) conducted a study on…

When a source has two authors, include both authors’ last names in the in-text citation, separated by “and.” For example:

[1] Smith and Johnson found that…

When a source has three or more authors, use the first author’s last name followed by “et al.” in the in-text citation. For example:

[2] Smith et al. conducted a study on…

Page Numbers in In-Text Citations

The use of page numbers in in-text citations is more peculiar to APA style. You can use paragraphs as indicated above if the source has no page, as seen in some e-books and websites.

Creating a Reference List or Bibliography

Creating a reference list is one of the most important tips for writing a research paper because it shows the general scheme of paper citation. This part of the content is a step-by-step process you can follow to create your reference list for your research paper.

Formatting and Organizing Your References

Formatting and organizing your references is the first step when you want to create your bibliography. You need to arrange all the full references to the in-text citation in the downward part of your paper. To avoid missing out on any, writing every full reference when you write the in-text citation is advisable.

Alphabetizing Your References

Alphabetizing your references ensures you create your bibliography in an orderly fashion for easy comprehension. Hence, you can do it numerically or alphabetically. The numerical order is dependent on the referencing system you are using, while the alphabetical order uses the author’s name to organize the reference.

Citations for Different Source Types

Different source types have their respective references, even for scientific papers. The commonest sources include books, journals, chapters, presentations, and online (to cite a website).

See how to cite an example for each source below:

Author, Initial. (Year). Book Title. City of publication, Country/State: Publisher.

“Social, M. (2023). The effect of the internet in this modern era . London, England: Ink.”

Author last name, First name. Book Title: Subtitle . Edition, Publisher, Year.

Donaldson, Bruce. Dutch: A Comprehensive Grammar . 3rd ed., Routledge, 2017..

Author last name, First name. Book Title: Subtitle . Edition. Place of publication: Publisher, Year. E-book format.

Donaldson, Bruce. Dutch: A Comprehensive Grammar . 3rd ed. Abingdon-on-Thames: Routledge, 2017.

  • N. Last Name, Title , Edition. City: Publisher, 2000.
  • Angelou, I Know Why the Caged Bird Sings , 1st ed. New York: Random House, 1969

Quote (Name Date)

Referencing is vital in research (Smith 2020).

Author, Initial. (Year). Article Title. Journal Title. The volume of the Journal (in italics), issue number of journal in round brackets, page range of articles, URL, and first time.

Social, M. (2023). The effect of the internet in this modern era . Digital Technology, 26(8), 22-24. (Insert URL).

Author. Journal title Date, Page. DOI

Ahmed, Sara. “What is Whiteness.” Feminist Theory , vol. 8, no. 2, Aug. 2007, pp. 149–168. https://doi.org/10.1177/1464700107078139.

Author’s Last Name, First Name. “Article Title.” Journal Name Volume, No. Issue (Month or Season Year): Page range. DOI or URL.

Pickard, Hanna. “What Is Personality Disorder?” Philosophy, Psychiatry, & Psychology 18, no. 3 (September 2011): 181–84. https://doi.org/10.1353/ppp.2011.0040.

Author Initial(s) and Surname, “Article title,” Journal Title , volume number, issue number, page range, month, and year of publication.

  • Chesum, “Innovations in Catalyzation,” J Adhes Sci Technol , Vol. 7, No. 1., pp. 11–24, July-September 2012.

Author Surname, Author Forename. Year Published. ‘Title’. Publication Title Volume Number (Issue Number): Pages Used. Retrieved October 10, 2013 (http://Website URL).

Sandelowski, Margarete. 1994. ‘Focus On Qualitative Methods. Notes On Transcription’. Research in Nursing \& Health 17(4):312.

Chapter Author’s Last Name, First Initial. Second Initial. (Year). Chapter or article title. Editor First Initial. Second Initial. Editor’s Last Name (Ed.). Book title: Subtitle (edition number, if not the first pages of the chapter). Location of publication: Publisher.

Social, M.O., (2023). Coarctation. In D.S. Moodie (Ed.). Management of heart disease: Indulthood (pp. 142-170). Minneapolis, Minnesota: Cardiotext Publishing.

Name. Book title: Subtitle. Editors. Location of publication: publisher.

Schwartz, Paula. “Redefining Resistance: Women in France.” Behind the Lines: Two World Wars , edited by Margaret R. Higonnet et al., Yale UP, 1987, pp. 141–53.

Author’s Last Name, First Name. “Chapter Title.” In Book Title: Subtitle , edited by Editor first name Last name, Page range. Place of publication: Publisher, Year.

Nussbaum, Martha C. “Legal Reasoning.” In The Cambridge Law , edited by John Tasioulas, 59–77. Cambridge: Cambridge University Press, 2020.

Author(s), “Chapter title,” in Book Title, Editor(s), Ed(s). City, Country: Publisher, year, p(p). page(s).

  • Saito, A. Jorio, and M. S. Dresselhaus, “Properties of nanographene,” in The Oxford Book of Technology, vol. 2, Materials , A. V. NarlikarEds. Oxford, U.K.: Oxford Univ. Press, 2010, pp. 1–30.

Author’s Last Name, First Name. Year of publication. “Title of Chapter.” Pp. Numbers in Title of Book (italicized), edited by F.I. MI. Last. Location of publisher, state or province postal code or name of country (if a foreign publisher): Publisher’s Name.

Rubin, Avi. 2015. “The Slave: A Drama from the Last Century.” Pp. 87-103 in Society, Culture in Asia: The Modernities , edited by E. R. Toledano: Walter De Gruyter Incorporated.

Conference Paper/Presentation

Last name, initial (Year). Conference paper title. Editor initial, last name (Ed.), Proceedings Book Title . Place of Publication: Publisher.

Winstone, N. & Boud, D. (2017). Supporting students’ engagement: the adoption of practices in the U.K. and Australia. A nnual Conference . Newport, South Wales

Surname, First Name. “Paper Title.” Proceedings Title, Conference Location and Date , edited by Editor Name(s), Publisher, Date of Publication.

Lewis, Jack. “Literature: The Consequences of Loss.” Library Proceedings Conference, Amsterdam, 13–14 June , edited by W. Oldham, LCP Publications, 2015.

Author First Name Last Name, “Title of the Paper” (paper presentation, Conference, Location, Date of conference).

Allison Cloyd, “An Examination of College Students” (paper presentation, EasyBib Conference, New York, NY, July 30, 2014) .

Author initials. Last name, Book Title . City, Country: Publisher, Year.

  • P. Hailman, Coding: Man-Made Signals . Cambridge: Harvard Univ. Press, 2008.

Author Surname, Author Forename. Year Published. ‘Title’. P. Pages Used in Publication Title . City: Publisher. Retrieved October 10, 2013 (http://Website URL).

Vargas, Jose. 2014. ‘The End Of Liberty’. Pp. 40-42 in The end . Buenos Aires: Elsevier.

Online Sources

Last Name, Initials. (Year, Month Day). Article title . Site Name. URL

The countdown: A prophecy takedown . (2020, October 19). BBC News. https://www.bbc.com/news/election-us-2020-54596667

Author’s Last Name, First Name. Title of Book . Edition, Publisher, Year of publication.

Smith, Thomas. The Citation Manual for Students: A Guide . 2nd ed., Wiley, 2020.

Author First and Last Name, Title of Book (Place of publication: publisher, year), page number(s).

Albert Einstein, The Meaning of Relativity (Princeton: Princeton University Press, 1923), 44–45.

Author initials. Last Name, Book Title . City (and state if in the U.S.), Country: Publisher, Year.

  • P. Hailman, Redundancy: Man-Made Signals . Cambridge, MA, USA: Harvard Univ. Press, 2008.

Last Name, First M. Year. “Title of article.” Title of Journal volume (issue): pages.

DOI/Retrieved Month Day, Year (URL)

Granello, Paul F. 1999. “College Students’ Wellness Due to Social Support.” Journal of Counseling 2(2):110-120.

Doi: 10.1002/j.2161-1882.1999.tb00149.x.

Tips for Accuracy

The goal of citing your paper is because of the advantages stated above. As such, you should not negotiate the accuracy of your citation. Here are the tips you can follow for accurate referencing:

Verify Your Source

Confirm if your source is credible or not. It is easier to verify books, journal articles, and chapters. You should check multiple links to confirm their authenticity.

Follow the One Style Guide

Maintain a single referencing style throughout your paper. It is improper to employ multiple referencing styles. If not specified, you can consider the APA style.

Verify DOI and URLs

DOI and URLs can be tricky and sensitive. A simple error with the punctuation can make them invalid. Hence, verifying every DOI and URL with a click is advisable. Discrediting your citation format for a scientific research paper reference based on an invalid URL is not worth it.

Online Citation Generators

Thanks to the digital age, you don’t have to worry about manually compiling your reference or generating its in-text citation. You can employ online generators to do the rough work for you. In turn, you will have more time to focus on the major content of your research work.

Use University Libraries and Writing Centers

Libraries and writing centers have extensive collections of cited sources. Since books, publications, and journals are more credible sources, university libraries remain a valid source to increase the credibility of your paper.

Leave No Stone Unturned!

Referencing and citation are the best way to preserve the relevance of your academic paper. It gives it the appropriate credibility for future use. That means another writer can refer to your work over many years, even when the level of advancement may be unmatched. A well-referenced work is evergreen.

One must note that well-oriented research paper citations have a proper format. The options include APA, MLA (citation style for science), Chicago, IEEE, and ASA. If not stated, it is advisable to follow the APA formatting style, as it is the most common. However, stick with formatting while compiling cited sources for a research paper.

Readers also enjoyed

MLA Style Essay Made Easy: Walkthrough of MLA Formatting

WHY WAIT? PLACE AN ORDER RIGHT NOW!

Just fill out the form, press the button, and have no worries!

We use cookies to give you the best experience possible. By continuing we’ll assume you board with our cookie policy.

how write reference research paper

how write reference research paper

How To Write References for Academic & Scientific Research Papers

How To Write References for Academic and Scientific Research Papers Writing accurate & appropriate references is an essential aspect of preparing a research paper for successful publication, examination or any other kind of serious dissemination or evaluation. This article explains exactly how to write perfect references in two widely used scholarly styles: the parenthetical author–date system recommended by the American Psychological Association (APA) & the sequential numerical or Vancouver system frequently used in the sciences. The post also includes several clear examples of in-text citations & complete bibliographical references formatted in both styles. Neither of these documentation styles is inherently complex, though each does have its characteristic pitfalls, and the utmost accuracy is essential when using either. Accusations of plagiarism or misrepresentation of the work of other scholars can be the unpleasant result if authors are not absolutely correct and scrupulously thorough in providing citations and references when they should to acknowledge the research of others. In addition, publication attempts can prove unsuccessful and grades lower than expected if instructions and guidelines for references are not observed with precision and consistency. The discussion and examples offered below outline exactly how to provide scholarly references for articles and books in one version of an author–date documentation style – APA – and one of a numerical style – Vancouver – but do be aware that various versions of these two basic styles exist, so consulting the guidelines, instructions or manual specific to the research paper you are writing is always imperative before finalising formats for in-text citations and complete references. PhD Thesis Editing Services Writing APA Author–Date References for a Research Paper Writing an accurate and appropriate APA author–date reference is a two-stage process involving 1) the creation of an in-text citation in the main body of the paper and 2) the addition of a complete bibliographical entry about the source in a list of references at the end of the paper.

1. The in-text citation should contain the last name of the author (or last names of the authors if there is more than one) who wrote the article, book or other document followed by the document’s date of publication. This information most frequently appears in parentheses immediately after the statement related to the paper, as in this example: • A recent study of the text presents a similar argument (Wilson & Bond, 2016). Alternatively, the names of the authors or the date of publication can be integrated into the main text, with the remaining information presented in parentheses: • Wilson and Bond present a similar argument in their recent study of the text (2016). • A 2016 examination of the text presents a similar argument (Wilson & Bond). Rewording of the main text is obviously necessary, but the only difference (beyond arrangement) in the citation information itself is that the word ‘and’ is used between the author names in the main text, whereas an ampersand (&) is used between those names when they appear in parentheses. The parentheses can sometimes be eliminated altogether by writing both author names and publication date in the main text: • Wilson and Bond’s 2016 study of the text presents a similar argument. Page numbers can be used for referring to specific information in particular parts of a publication, but they are usually only required in APA style for direct quotations when a passage or other part of a published document is reproduced word for word in a new research paper. In such cases, the page number is separated from the publication date by a comma and preceded by the abbreviation ‘p.’ for ‘page’: • As Wilson and Bond explain, ‘the political reading of the text, even the most personal of its episodes, seems universal until the book falls into a woman’s hands’ (2016, p.88).

When two or more sources are cited in the same set of parentheses, semicolons are used to separate the sources: • Both studies consider the poem in relation to urban culture (Samuel & Watson, 2013; Wilson & Bond, 2016). The normal arrangement when multiple sources are cited in a single set of parentheses is to observe alphabetical order according to the author names, as I have done above (with ‘Samuel’ preceding ‘Wilson’). Notice that the in-text citation takes the same form whether the source cited is a book or an article, with ‘Samuel & Watson’ referring here to a monograph and ‘Wilson & Bond’ to a journal article. PhD Thesis Editing Services 2. Every source cited in the text of an academic or scientific research paper using APA style should also be included in a list that is entitled ‘References’ and presented at the end of the paper. An APA list of references should be arranged alphabetically based on author names, and all the bibliographical information required for readers to find each source must be provided in a specific format. The author names for a publication come first and are inverted, with the last name of the first author of each document opening the bibliographical entry. Author names are followed by the date of publication (in parentheses), with these two pieces of information serving readers by connecting the complete reference to the in-text citation. It is therefore vital that the last names of authors and the publication dates provided in both places are checked against each other for errors and inconsistencies and then carefully corrected to agree with precision.

For the complete reference to a journal article, the title of the article follows the date of publication. The name and volume number of the journal come next, both of them in italic font, though do be aware that special fonts may not be displayed in this post. The pages on which the article can be found come next, and if there is a doi or url for an online version of the paper, that should be the last item in the entry, which would take this form: • Wilson, S., & Bond, F. (2016). Political and personal readings of the earliest zone poem. Urban Poetry, 12, 72–94. doi:00.0000/00000000000000 For the complete reference to a book, the information, and thus the format, is a little different. The title of the book follows the publication date and appears in italic font, with the place of publication and publisher’s name completing the reference: • Samuel, H., & Watson, M. (2013). Political poetry and modern urbanity. London: Big City Press.

Writing Sequential Numerical References for a Research Paper The same two-step process is necessary when writing the sequential numerical references used for Vancouver style documentation, but in-text citations are notably simpler, a different arrangement is used for the list of references and a somewhat different format is required for the complete bibliographical entries included in the list.

1. For a numerical in-text citation, a single Arabic numeral is all that is required. Each source is assigned a number when it is first cited, so the sources used in a research paper are numbered sequentially according to the order of first citation, with each source retaining throughout the paper the number it was originally assigned. The first source cited would therefore be reference 1, the second reference 2 and so on. The International Committee of Medical Journal Editors (ICMJE) recommends placing these reference numbers in parentheses, with a citation taking this form: • A recent study of the text presents a similar argument (1). As is the case with author–date citations, information about sources can also be added in the main text: • Wilson and Bond present a similar argument in their recent study of the text (1). • A 2016 examination of the text presents a similar argument (1). • Wilson and Bond’s 2016 study of the text presents a similar argument (1). Unlike author–date citations, however, this additional information in the text does not negate the need for the reference number, which is always required.

If you need to cite a specific page of a document to point readers to a particular piece of information or indicate the location of a quoted passage, the page number should be added after the reference number, usually with a comma to separate it from the reference number and a preceding ‘p.’ to avoid confusion: • As Wilson and Bond explain, ‘the political reading of the text, even the most personal of its episodes, seems universal until the book falls into a woman’s hands’ (1, p.88). When two or more sources are cited at the same time, commas are generally used to separate the reference numbers, usually without intervening spaces: • Several studies have taken this approach to the text (1,2,5–8). PhD Thesis Editing Services 2. The reference list for sequential numerical citations is arranged, not surprisingly, by the numerical sequence of the citations. This means that the first source cited in a research paper (reference 1) is also the first source listed in the References section of the paper, the second is the second source in the list and so on. The following two sample references follow ICMJE guidelines and would serve as the opening entries in a numerical list of references: • 1. Wilson S, Bond F. Political and personal readings of the earliest zone poem. Urban Poetry. 2016;12:72–94. doi:00.0000/00000000000000. • 2. Samuel H, Watson M. Political Poetry and Modern Urbanity. London: Big City Press; 2013.

As these examples show, the information required for a complete reference varies according to the nature of the source cited, just as it does with author–date references. In addition, the names of journals (but not books) are often abbreviated when preparing numerical references. It is essential, however, that the correct or standard abbreviation for each journal be used when shortening journal titles, which can easily be confused in their abbreviated forms, so a little research may be necessary to determine the right abbreviation. Use of the complete journal title is recommended when there is any doubt or there is no standard abbreviation. A cautionary note is in order when writing sequential numerical references. Adding or deleting sources from a numerical list of references that has been arranged according to the order in which sources are first cited can necessitate changes in subsequent list entries as well as in the in-text citations, and the same is the case with any changes to those in-text citations. The reason is simple: if, for example, you remove reference 3 from the text or list, what was reference 4 becomes reference 3, what was reference 5 becomes reference 4 and so on. If you add that removed reference back in elsewhere more alterations will ensue. It is therefore wise to check and finalise the order of the reference list very carefully indeed after all the in-text citations are in their final places, and to ensure that the assigned reference numbers agree with the utmost accuracy between in-text citations and the list of references.

Why Our Editing and Proofreading Services? At Proof-Reading-Service.com we offer the highest quality journal article editing , phd thesis editing and proofreading services via our large and extremely dedicated team of academic and scientific professionals. All of our proofreaders are native speakers of English who have earned their own postgraduate degrees, and their areas of specialisation cover such a wide range of disciplines that we are able to help our international clientele with research editing to improve and perfect all kinds of academic manuscripts for successful publication. Many of the carefully trained members of our expert editing and proofreading team work predominantly on articles intended for publication in scholarly journals, applying painstaking journal editing standards to ensure that the references and formatting used in each paper are in conformity with the journal’s instructions for authors and to correct any grammar, spelling, punctuation or simple typing errors. In this way, we enable our clients to report their research in the clear and accurate ways required to impress acquisitions proofreaders and achieve publication.

Our scientific proofreading services for the authors of a wide variety of scientific journal papers are especially popular, but we also offer manuscript proofreading services and have the experience and expertise to proofread and edit manuscripts in all scholarly disciplines, as well as beyond them. We have team members who specialise in medical proofreading services , and some of our experts dedicate their time exclusively to PhD proofreading and master’s proofreading , offering research students the opportunity to improve their use of formatting and language through the most exacting PhD thesis editing and dissertation proofreading practices. Whether you are preparing a conference paper for presentation, polishing a progress report to share with colleagues, or facing the daunting task of editing and perfecting any kind of scholarly document for publication, a qualified member of our professional team can provide invaluable assistance and give you greater confidence in your written work.

If you are in the process of preparing an article for an academic or scientific journal, or planning one for the near future, you may well be interested in a new book, Guide to Journal Publication , which is available on our Tips and Advice on Publishing Research in Journals website.

Guide to Academic and Scientific Publication

How to get your writing published in scholarly journals.

It provides practical advice on planning, preparing and submitting articles for publication in scholarly journals.

PhD Success

How to write a doctoral thesis.

If you are in the process of preparing a PhD thesis for submission, or planning one for the near future, you may well be interested in the book, How to Write a Doctoral Thesis , which is available on our thesis proofreading website.

PhD Success: How to Write a Doctoral Thesis provides guidance for students familiar with English and the procedures of English universities, but it also acknowledges that many theses in the English language are now written by candidates whose first language is not English, so it carefully explains the scholarly styles, conventions and standards expected of a successful doctoral thesis in the English language.

Why Is Proofreading Important?

To improve the quality of papers.

Effective proofreading is absolutely vital to the production of high-quality scholarly and professional documents. When done carefully, correctly and thoroughly, proofreading can make the difference between writing that communicates successfully with its intended readers and writing that does not. No author creates a perfect text without reviewing, reflecting on and revising what he or she has written, and proofreading is an extremely important part of this process.

topbanner errow

  • Privacy Policy
  • SignUp/Login

Research Method

Home » Research Paper – Structure, Examples and Writing Guide

Research Paper – Structure, Examples and Writing Guide

Table of Contents

Research Paper

Research Paper

Definition:

Research Paper is a written document that presents the author’s original research, analysis, and interpretation of a specific topic or issue.

It is typically based on Empirical Evidence, and may involve qualitative or quantitative research methods, or a combination of both. The purpose of a research paper is to contribute new knowledge or insights to a particular field of study, and to demonstrate the author’s understanding of the existing literature and theories related to the topic.

Structure of Research Paper

The structure of a research paper typically follows a standard format, consisting of several sections that convey specific information about the research study. The following is a detailed explanation of the structure of a research paper:

The title page contains the title of the paper, the name(s) of the author(s), and the affiliation(s) of the author(s). It also includes the date of submission and possibly, the name of the journal or conference where the paper is to be published.

The abstract is a brief summary of the research paper, typically ranging from 100 to 250 words. It should include the research question, the methods used, the key findings, and the implications of the results. The abstract should be written in a concise and clear manner to allow readers to quickly grasp the essence of the research.

Introduction

The introduction section of a research paper provides background information about the research problem, the research question, and the research objectives. It also outlines the significance of the research, the research gap that it aims to fill, and the approach taken to address the research question. Finally, the introduction section ends with a clear statement of the research hypothesis or research question.

Literature Review

The literature review section of a research paper provides an overview of the existing literature on the topic of study. It includes a critical analysis and synthesis of the literature, highlighting the key concepts, themes, and debates. The literature review should also demonstrate the research gap and how the current study seeks to address it.

The methods section of a research paper describes the research design, the sample selection, the data collection and analysis procedures, and the statistical methods used to analyze the data. This section should provide sufficient detail for other researchers to replicate the study.

The results section presents the findings of the research, using tables, graphs, and figures to illustrate the data. The findings should be presented in a clear and concise manner, with reference to the research question and hypothesis.

The discussion section of a research paper interprets the findings and discusses their implications for the research question, the literature review, and the field of study. It should also address the limitations of the study and suggest future research directions.

The conclusion section summarizes the main findings of the study, restates the research question and hypothesis, and provides a final reflection on the significance of the research.

The references section provides a list of all the sources cited in the paper, following a specific citation style such as APA, MLA or Chicago.

How to Write Research Paper

You can write Research Paper by the following guide:

  • Choose a Topic: The first step is to select a topic that interests you and is relevant to your field of study. Brainstorm ideas and narrow down to a research question that is specific and researchable.
  • Conduct a Literature Review: The literature review helps you identify the gap in the existing research and provides a basis for your research question. It also helps you to develop a theoretical framework and research hypothesis.
  • Develop a Thesis Statement : The thesis statement is the main argument of your research paper. It should be clear, concise and specific to your research question.
  • Plan your Research: Develop a research plan that outlines the methods, data sources, and data analysis procedures. This will help you to collect and analyze data effectively.
  • Collect and Analyze Data: Collect data using various methods such as surveys, interviews, observations, or experiments. Analyze data using statistical tools or other qualitative methods.
  • Organize your Paper : Organize your paper into sections such as Introduction, Literature Review, Methods, Results, Discussion, and Conclusion. Ensure that each section is coherent and follows a logical flow.
  • Write your Paper : Start by writing the introduction, followed by the literature review, methods, results, discussion, and conclusion. Ensure that your writing is clear, concise, and follows the required formatting and citation styles.
  • Edit and Proofread your Paper: Review your paper for grammar and spelling errors, and ensure that it is well-structured and easy to read. Ask someone else to review your paper to get feedback and suggestions for improvement.
  • Cite your Sources: Ensure that you properly cite all sources used in your research paper. This is essential for giving credit to the original authors and avoiding plagiarism.

Research Paper Example

Note : The below example research paper is for illustrative purposes only and is not an actual research paper. Actual research papers may have different structures, contents, and formats depending on the field of study, research question, data collection and analysis methods, and other factors. Students should always consult with their professors or supervisors for specific guidelines and expectations for their research papers.

Research Paper Example sample for Students:

Title: The Impact of Social Media on Mental Health among Young Adults

Abstract: This study aims to investigate the impact of social media use on the mental health of young adults. A literature review was conducted to examine the existing research on the topic. A survey was then administered to 200 university students to collect data on their social media use, mental health status, and perceived impact of social media on their mental health. The results showed that social media use is positively associated with depression, anxiety, and stress. The study also found that social comparison, cyberbullying, and FOMO (Fear of Missing Out) are significant predictors of mental health problems among young adults.

Introduction: Social media has become an integral part of modern life, particularly among young adults. While social media has many benefits, including increased communication and social connectivity, it has also been associated with negative outcomes, such as addiction, cyberbullying, and mental health problems. This study aims to investigate the impact of social media use on the mental health of young adults.

Literature Review: The literature review highlights the existing research on the impact of social media use on mental health. The review shows that social media use is associated with depression, anxiety, stress, and other mental health problems. The review also identifies the factors that contribute to the negative impact of social media, including social comparison, cyberbullying, and FOMO.

Methods : A survey was administered to 200 university students to collect data on their social media use, mental health status, and perceived impact of social media on their mental health. The survey included questions on social media use, mental health status (measured using the DASS-21), and perceived impact of social media on their mental health. Data were analyzed using descriptive statistics and regression analysis.

Results : The results showed that social media use is positively associated with depression, anxiety, and stress. The study also found that social comparison, cyberbullying, and FOMO are significant predictors of mental health problems among young adults.

Discussion : The study’s findings suggest that social media use has a negative impact on the mental health of young adults. The study highlights the need for interventions that address the factors contributing to the negative impact of social media, such as social comparison, cyberbullying, and FOMO.

Conclusion : In conclusion, social media use has a significant impact on the mental health of young adults. The study’s findings underscore the need for interventions that promote healthy social media use and address the negative outcomes associated with social media use. Future research can explore the effectiveness of interventions aimed at reducing the negative impact of social media on mental health. Additionally, longitudinal studies can investigate the long-term effects of social media use on mental health.

Limitations : The study has some limitations, including the use of self-report measures and a cross-sectional design. The use of self-report measures may result in biased responses, and a cross-sectional design limits the ability to establish causality.

Implications: The study’s findings have implications for mental health professionals, educators, and policymakers. Mental health professionals can use the findings to develop interventions that address the negative impact of social media use on mental health. Educators can incorporate social media literacy into their curriculum to promote healthy social media use among young adults. Policymakers can use the findings to develop policies that protect young adults from the negative outcomes associated with social media use.

References :

  • Twenge, J. M., & Campbell, W. K. (2019). Associations between screen time and lower psychological well-being among children and adolescents: Evidence from a population-based study. Preventive medicine reports, 15, 100918.
  • Primack, B. A., Shensa, A., Escobar-Viera, C. G., Barrett, E. L., Sidani, J. E., Colditz, J. B., … & James, A. E. (2017). Use of multiple social media platforms and symptoms of depression and anxiety: A nationally-representative study among US young adults. Computers in Human Behavior, 69, 1-9.
  • Van der Meer, T. G., & Verhoeven, J. W. (2017). Social media and its impact on academic performance of students. Journal of Information Technology Education: Research, 16, 383-398.

Appendix : The survey used in this study is provided below.

Social Media and Mental Health Survey

  • How often do you use social media per day?
  • Less than 30 minutes
  • 30 minutes to 1 hour
  • 1 to 2 hours
  • 2 to 4 hours
  • More than 4 hours
  • Which social media platforms do you use?
  • Others (Please specify)
  • How often do you experience the following on social media?
  • Social comparison (comparing yourself to others)
  • Cyberbullying
  • Fear of Missing Out (FOMO)
  • Have you ever experienced any of the following mental health problems in the past month?
  • Do you think social media use has a positive or negative impact on your mental health?
  • Very positive
  • Somewhat positive
  • Somewhat negative
  • Very negative
  • In your opinion, which factors contribute to the negative impact of social media on mental health?
  • Social comparison
  • In your opinion, what interventions could be effective in reducing the negative impact of social media on mental health?
  • Education on healthy social media use
  • Counseling for mental health problems caused by social media
  • Social media detox programs
  • Regulation of social media use

Thank you for your participation!

Applications of Research Paper

Research papers have several applications in various fields, including:

  • Advancing knowledge: Research papers contribute to the advancement of knowledge by generating new insights, theories, and findings that can inform future research and practice. They help to answer important questions, clarify existing knowledge, and identify areas that require further investigation.
  • Informing policy: Research papers can inform policy decisions by providing evidence-based recommendations for policymakers. They can help to identify gaps in current policies, evaluate the effectiveness of interventions, and inform the development of new policies and regulations.
  • Improving practice: Research papers can improve practice by providing evidence-based guidance for professionals in various fields, including medicine, education, business, and psychology. They can inform the development of best practices, guidelines, and standards of care that can improve outcomes for individuals and organizations.
  • Educating students : Research papers are often used as teaching tools in universities and colleges to educate students about research methods, data analysis, and academic writing. They help students to develop critical thinking skills, research skills, and communication skills that are essential for success in many careers.
  • Fostering collaboration: Research papers can foster collaboration among researchers, practitioners, and policymakers by providing a platform for sharing knowledge and ideas. They can facilitate interdisciplinary collaborations and partnerships that can lead to innovative solutions to complex problems.

When to Write Research Paper

Research papers are typically written when a person has completed a research project or when they have conducted a study and have obtained data or findings that they want to share with the academic or professional community. Research papers are usually written in academic settings, such as universities, but they can also be written in professional settings, such as research organizations, government agencies, or private companies.

Here are some common situations where a person might need to write a research paper:

  • For academic purposes: Students in universities and colleges are often required to write research papers as part of their coursework, particularly in the social sciences, natural sciences, and humanities. Writing research papers helps students to develop research skills, critical thinking skills, and academic writing skills.
  • For publication: Researchers often write research papers to publish their findings in academic journals or to present their work at academic conferences. Publishing research papers is an important way to disseminate research findings to the academic community and to establish oneself as an expert in a particular field.
  • To inform policy or practice : Researchers may write research papers to inform policy decisions or to improve practice in various fields. Research findings can be used to inform the development of policies, guidelines, and best practices that can improve outcomes for individuals and organizations.
  • To share new insights or ideas: Researchers may write research papers to share new insights or ideas with the academic or professional community. They may present new theories, propose new research methods, or challenge existing paradigms in their field.

Purpose of Research Paper

The purpose of a research paper is to present the results of a study or investigation in a clear, concise, and structured manner. Research papers are written to communicate new knowledge, ideas, or findings to a specific audience, such as researchers, scholars, practitioners, or policymakers. The primary purposes of a research paper are:

  • To contribute to the body of knowledge : Research papers aim to add new knowledge or insights to a particular field or discipline. They do this by reporting the results of empirical studies, reviewing and synthesizing existing literature, proposing new theories, or providing new perspectives on a topic.
  • To inform or persuade: Research papers are written to inform or persuade the reader about a particular issue, topic, or phenomenon. They present evidence and arguments to support their claims and seek to persuade the reader of the validity of their findings or recommendations.
  • To advance the field: Research papers seek to advance the field or discipline by identifying gaps in knowledge, proposing new research questions or approaches, or challenging existing assumptions or paradigms. They aim to contribute to ongoing debates and discussions within a field and to stimulate further research and inquiry.
  • To demonstrate research skills: Research papers demonstrate the author’s research skills, including their ability to design and conduct a study, collect and analyze data, and interpret and communicate findings. They also demonstrate the author’s ability to critically evaluate existing literature, synthesize information from multiple sources, and write in a clear and structured manner.

Characteristics of Research Paper

Research papers have several characteristics that distinguish them from other forms of academic or professional writing. Here are some common characteristics of research papers:

  • Evidence-based: Research papers are based on empirical evidence, which is collected through rigorous research methods such as experiments, surveys, observations, or interviews. They rely on objective data and facts to support their claims and conclusions.
  • Structured and organized: Research papers have a clear and logical structure, with sections such as introduction, literature review, methods, results, discussion, and conclusion. They are organized in a way that helps the reader to follow the argument and understand the findings.
  • Formal and objective: Research papers are written in a formal and objective tone, with an emphasis on clarity, precision, and accuracy. They avoid subjective language or personal opinions and instead rely on objective data and analysis to support their arguments.
  • Citations and references: Research papers include citations and references to acknowledge the sources of information and ideas used in the paper. They use a specific citation style, such as APA, MLA, or Chicago, to ensure consistency and accuracy.
  • Peer-reviewed: Research papers are often peer-reviewed, which means they are evaluated by other experts in the field before they are published. Peer-review ensures that the research is of high quality, meets ethical standards, and contributes to the advancement of knowledge in the field.
  • Objective and unbiased: Research papers strive to be objective and unbiased in their presentation of the findings. They avoid personal biases or preconceptions and instead rely on the data and analysis to draw conclusions.

Advantages of Research Paper

Research papers have many advantages, both for the individual researcher and for the broader academic and professional community. Here are some advantages of research papers:

  • Contribution to knowledge: Research papers contribute to the body of knowledge in a particular field or discipline. They add new information, insights, and perspectives to existing literature and help advance the understanding of a particular phenomenon or issue.
  • Opportunity for intellectual growth: Research papers provide an opportunity for intellectual growth for the researcher. They require critical thinking, problem-solving, and creativity, which can help develop the researcher’s skills and knowledge.
  • Career advancement: Research papers can help advance the researcher’s career by demonstrating their expertise and contributions to the field. They can also lead to new research opportunities, collaborations, and funding.
  • Academic recognition: Research papers can lead to academic recognition in the form of awards, grants, or invitations to speak at conferences or events. They can also contribute to the researcher’s reputation and standing in the field.
  • Impact on policy and practice: Research papers can have a significant impact on policy and practice. They can inform policy decisions, guide practice, and lead to changes in laws, regulations, or procedures.
  • Advancement of society: Research papers can contribute to the advancement of society by addressing important issues, identifying solutions to problems, and promoting social justice and equality.

Limitations of Research Paper

Research papers also have some limitations that should be considered when interpreting their findings or implications. Here are some common limitations of research papers:

  • Limited generalizability: Research findings may not be generalizable to other populations, settings, or contexts. Studies often use specific samples or conditions that may not reflect the broader population or real-world situations.
  • Potential for bias : Research papers may be biased due to factors such as sample selection, measurement errors, or researcher biases. It is important to evaluate the quality of the research design and methods used to ensure that the findings are valid and reliable.
  • Ethical concerns: Research papers may raise ethical concerns, such as the use of vulnerable populations or invasive procedures. Researchers must adhere to ethical guidelines and obtain informed consent from participants to ensure that the research is conducted in a responsible and respectful manner.
  • Limitations of methodology: Research papers may be limited by the methodology used to collect and analyze data. For example, certain research methods may not capture the complexity or nuance of a particular phenomenon, or may not be appropriate for certain research questions.
  • Publication bias: Research papers may be subject to publication bias, where positive or significant findings are more likely to be published than negative or non-significant findings. This can skew the overall findings of a particular area of research.
  • Time and resource constraints: Research papers may be limited by time and resource constraints, which can affect the quality and scope of the research. Researchers may not have access to certain data or resources, or may be unable to conduct long-term studies due to practical limitations.

About the author

' src=

Muhammad Hassan

Researcher, Academic Writer, Web developer

You may also like

Research Paper Conclusion

Research Paper Conclusion – Writing Guide and...

Appendices

Appendices – Writing Guide, Types and Examples

Research Paper Citation

How to Cite Research Paper – All Formats and...

Research Report

Research Report – Example, Writing Guide and...

Delimitations

Delimitations in Research – Types, Examples and...

Scope of the Research

Scope of the Research – Writing Guide and...

Grad Coach (R)

What’s Included: Research Paper Template

If you’re preparing to write an academic research paper, our free research paper template is the perfect starting point. In the template, we cover every section step by step, with clear, straightforward explanations and examples .

The template’s structure is based on the tried and trusted best-practice format for formal academic research papers. The template structure reflects the overall research process, ensuring your paper will have a smooth, logical flow from chapter to chapter.

The research paper template covers the following core sections:

  • The title page/cover page
  • Abstract (sometimes also called the executive summary)
  • Section 1: Introduction 
  • Section 2: Literature review 
  • Section 3: Methodology
  • Section 4: Findings /results
  • Section 5: Discussion
  • Section 6: Conclusion
  • Reference list

Each section is explained in plain, straightforward language , followed by an overview of the key elements that you need to cover within each section. We’ve also included links to free resources to help you understand how to write each section.

The cleanly formatted Google Doc can be downloaded as a fully editable MS Word Document (DOCX format), so you can use it as-is or convert it to LaTeX.

FAQs: Research Paper Template

What format is the template (doc, pdf, ppt, etc.).

The research paper template is provided as a Google Doc. You can download it in MS Word format or make a copy to your Google Drive. You’re also welcome to convert it to whatever format works best for you, such as LaTeX or PDF.

What types of research papers can this template be used for?

The template follows the standard best-practice structure for formal academic research papers, so it is suitable for the vast majority of degrees, particularly those within the sciences.

Some universities may have some additional requirements, but these are typically minor, with the core structure remaining the same. Therefore, it’s always a good idea to double-check your university’s requirements before you finalise your structure.

Is this template for an undergrad, Masters or PhD-level research paper?

This template can be used for a research paper at any level of study. It may be slight overkill for an undergraduate-level study, but it certainly won’t be missing anything.

How long should my research paper be?

This depends entirely on your university’s specific requirements, so it’s best to check with them. We include generic word count ranges for each section within the template, but these are purely indicative. 

What about the research proposal?

If you’re still working on your research proposal, we’ve got a template for that here .

We’ve also got loads of proposal-related guides and videos over on the Grad Coach blog .

How do I write a literature review?

We have a wealth of free resources on the Grad Coach Blog that unpack how to write a literature review from scratch. You can check out the literature review section of the blog here.

How do I create a research methodology?

We have a wealth of free resources on the Grad Coach Blog that unpack research methodology, both qualitative and quantitative. You can check out the methodology section of the blog here.

Can I share this research paper template with my friends/colleagues?

Yes, you’re welcome to share this template. If you want to post about it on your blog or social media, all we ask is that you reference this page as your source.

Can Grad Coach help me with my research paper?

Within the template, you’ll find plain-language explanations of each section, which should give you a fair amount of guidance. However, you’re also welcome to consider our private coaching services .

Free Webinar: Literature Review 101

how write reference research paper

How to Write a Term Paper: 8 Expert Tips for Academic Success 2024

  • Natalie Cowles
  • February 14, 2024

How to Write a Term Paper: 8 Expert Tips for Academic Success 2024

The journey to writing an exceptional term paper is a marathon, not a sprint. It’s a process that tests your research, analytical, and writing skills, all rolled into one challenging assignment. 

But fear not! With the right approach and guidance, crafting a term paper can become not just a means to score high grades but also an opportunity to deepen your understanding of your subject matter and enhance your academic skills.

Table of Contents

1. Truly Knowing What the Assignment Is Asking of You

Truly Knowing What the Assignment Is Asking of You

The first step in navigating the term paper sea is to thoroughly understand the assignment. It may seem straightforward, but many students falter by diving into the research and writing without a clear understanding of what is expected. Read the instructions carefully. 

If anything is unclear, don’t hesitate to ask your professor for clarification or find here a site that may be able to help. Knowing the scope, topic, length, format, and deadline from the outset will set a strong foundation for your work.

2. Choosing a Topic

Selecting the right topic is crucial. It’s the seed from which your term paper will grow. Aim for a topic that is not only interesting to you but also appropriate for the scope of the assignment and your academic level. 

It should be specific enough to be manageable but broad enough to allow for comprehensive research. 

If you find yourself stuck at this stage, consult your professor or peers for suggestions. They can offer perspectives that might not have occurred to you.

3. Conducting Thorough Research

Conducting Thorough Research

Research is the backbone of your term paper. Begin by consulting a variety of sources, including books, academic journals, and reputable websites. Libraries, both physical and digital, are treasure troves of information. 

Utilize databases such as JSTOR or Google Scholar to find relevant academic papers. As you research, keep meticulous records of your sources. This will make citing your references easier and ensure your paper is grounded in credible information.

4. Crafting an Outline

An outline is your roadmap, guiding you through the writing process. It helps organize your thoughts and structure your paper logically. Start with a broad overview, then break down the main sections into more detailed subsections. 

This will help you identify areas that need more research or sections that are too complex and need simplification. An effective outline ensures that every part of your paper serves the overall argument or thesis statement.

5. Writing the Draft

Writing the Draft

With your outline in hand, it’s time to start writing. The introduction should hook the reader, present your thesis statement , and outline the structure of your paper. Each body paragraph should focus on a single idea or piece of evidence, supporting your thesis. 

Use transitions to smoothly navigate from one idea to the next, maintaining a coherent flow throughout. The conclusion should tie everything together, reinforcing your thesis and highlighting the significance of your findings.

The writing process is iterative. Don’t aim for perfection on the first draft. Focus on getting your ideas down on paper; refinement comes later.

6. Revising and Editing

The difference between a good term paper and a great one often lies in the revision stage. Start by reviewing your paper for content and structure. 

Ensure each paragraph contributes to your thesis and that your argument flows logically. Then, move on to editing for clarity, coherence, and conciseness. Pay attention to grammar, punctuation, and style. 

Tools like Grammarly or the Hemingway Editor can be invaluable but don’t rely on them completely. A manual review is irreplaceable.

Finally, check your citations and references. They should adhere to the required format, whether it’s APA , MLA, or Chicago. This not only lends credibility to your paper but also avoids the pitfalls of plagiarism.

7. Handling Feedback

Seek Feedback from Your Professor

If possible, seek feedback from your professor or peers before the final submission. They can offer insights you might have missed and suggest improvements. Be open to criticism; it’s an opportunity for growth, not a personal attack. Use the feedback to refine your paper further.

8. Final Touches and Submission

Before submitting your paper, give it one last review. Check for any errors you might have missed and ensure that it meets all the assignment requirements. Submit your paper with confidence, knowing you’ve put in your best effort.

How Can I Narrow Down a Broad Topic for My Term Paper?

Narrowing down a broad topic requires a bit of brainstorming and preliminary research. Start by reading general sources about your topic to identify specific themes, trends, or issues that interest you. 

Then, consider how these specific angles relate to the broader topic. It can also be helpful to discuss your ideas with your professor or classmates to gain different perspectives. Finally, formulate a research question or thesis statement that reflects the narrowed focus. This approach ensures your topic is manageable and tailored to the assignment’s scope.

What Strategies Can I Use if I’m Struggling to Find Sources for My Topic?

If you’re struggling to find sources, try altering your search terms or using synonyms to expand your search. Consult with a librarian, who can offer expert guidance on searching databases and may suggest resources you hadn’t considered. 

How Do I Balance My Own Ideas with Research Findings in My Term Paper?

How Do I Balance My Own Ideas with Research Findings in My Term Paper?

To balance your own ideas with research findings, start by clearly stating your thesis or main argument. Use research findings to support your ideas, citing evidence that backs up your points. However, don’t just present the research; analyze it. 

Discuss how the evidence supports your thesis, what it means in the context of your argument, and any limitations or counterarguments. Your own analysis and synthesis of the research are what will make your term paper unique and insightful.

Can I Include Visuals in My Term Paper, and How Should I Do So?

Yes, visuals such as graphs, charts, and images can be included in your term paper to support your arguments or illustrate complex ideas. Ensure that each visual is clearly labeled (e.g., Figure 1, Table 1) and accompanied by a caption explaining what it shows.

Refer to the visuals in your text to guide the reader’s attention to them at relevant points in your argument. Always cite the source of the visual in accordance with the citation style you are using.

How Do I Handle Contradictory Evidence in My Term Paper?

Handling contradictory evidence is a crucial part of demonstrating critical thinking . Present the contradictory evidence fairly and objectively, then provide an analysis that explains why it does not undermine your thesis. 

You can argue that the evidence is flawed, outdated, or limited in scope. Alternatively, you can acknowledge the complexity of the issue and refine your thesis to accommodate the nuanced view that emerges from considering all evidence. This approach shows that you have engaged deeply with the material and strengthens your argument.

How Long Should I Spend on Each Stage of Writing My Term Paper?

How Long Should I Spend on Each Stage of Writing My Term Paper?

The time spent on each stage of writing a term paper can vary based on the length of the paper, the complexity of the topic, and your own working style. A balanced approach might involve spending 20% of your time on choosing a topic and conducting initial research, 30% on in-depth research and organizing your findings, 25% on writing the first draft, and 25% on revising, editing, and finalizing the paper.

Adjust these percentages based on your specific needs and deadlines. Remember, starting early and allocating time for each stage can help reduce stress and improve the quality of your work.

Final Words

Writing a term paper is a substantial academic endeavor, but it’s also a deeply rewarding one. It challenges you to think critically, research deeply, and express your thoughts clearly and coherently. By following these steps, you equip yourself with a structured approach to tackle this challenge head-on. 

Remember, academic writing is a skill honed over time. Each term paper is an opportunity to improve, learn, and grow as a scholar. Embrace the process, and you’ll find yourself not just surviving but thriving in the academic world.

  • Academic Writing , Assignment , Education , Research , Students , Term Paper , Tips

Lastest Posts

Sebastian Joe’s Ice Cream

How Pleasure is Made – Sebastian Joe’s Ice Cream

Unusual World of Asian Groceries - Asian Cuisine

The Unusual World of Asian Groceries – Do-It-Yourself Part of Eat Street

Mary Strickland - Improvisational Life - Short Bio

An Improvisational Life – Life and Work of Mary Strickland

City Council Passes Fossil Fuel Divestment Resolution

City Council Passes Fossil Fuel Divestment Resolution: City Goes Green

Minneapolis Joins CNCA

Minneapolis Joins Alliance Committed to Curbing Greenhouse Gases

Dog - Lyme’s Disease - Prevention, Tips and medicine

What to Do if Your Dog Has Been Exposed to Lyme’s Disease – Doctors Tips

Affiliate disclaimer.

Southwestjournal.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com. Amazon, the Amazon logo, AmazonSupply, and the AmazonSupply logo are trademarks of Amazon.com, Inc. or its affiliates.

How Do Independent Journalists Make Money? 9 Things to Know

How Do Independent Journalists Make Money? 9 Things to Know

NYC famous homes

40 Famous People that Live in New York 2024: Big City, Big Stars

Check out NYC's tallest buildings, like One World Trade Center and Central Park Tower, and see what makes each one stand out!

What Are the 13 Tallest Buildings in New York 2024? Touching the Clouds

tucker carlson net worth

Tucker Carlson Net Worth 2024: From Media To Inheritance

how write reference research paper

What Are The Lightest Basketball Shoes? 10 Best Performance Picks For 2024

Explore NBA position heights analyze player metrics and discover basketball trends How players measure up in 2024

Average NBA Height By Position 2024: How They Measure Up?

southwestjournal.com_logo

  • Editorial Policy
  • Privacy Policy
  • Terms and Conditions

Popular Categories

  • Celebrities

Who We Are?

  • Company: Shantel
  • Full Name: NEBOJŠA VUJINOVIĆ PR RAČUNARSKO PROGRAMIRANJE SHANTEL BEOGRAD (NOVI BEOGRAD)
  • Address: MILUTINA MILANKOVIĆA 90, 11070 NOVI BEOGRAD, Serbia
  • PIB/VAT Number: 112995998
  • Phone number: +381692564386
  • Email: [email protected]
  • Company Web: Shantel.co

© 2024 southwestjournal.com

Have a language expert improve your writing

Run a free plagiarism check in 10 minutes, generate accurate citations for free.

  • Knowledge Base
  • Research paper
  • Research Paper Format | APA, MLA, & Chicago Templates

Research Paper Format | APA, MLA, & Chicago Templates

Published on November 19, 2022 by Jack Caulfield . Revised on January 20, 2023.

The formatting of a research paper is different depending on which style guide you’re following. In addition to citations , APA, MLA, and Chicago provide format guidelines for things like font choices, page layout, format of headings and the format of the reference page.

Scribbr offers free Microsoft Word templates for the most common formats. Simply download and get started on your paper.

APA |  MLA | Chicago author-date | Chicago notes & bibliography

  • Generate an automatic table of contents
  • Generate a list of tables and figures
  • Ensure consistent paragraph formatting
  • Insert page numbering

Instantly correct all language mistakes in your text

Be assured that you'll submit flawless writing. Upload your document to correct all your mistakes.

upload-your-document-ai-proofreader

Table of contents

Formatting an apa paper, formatting an mla paper, formatting a chicago paper, frequently asked questions about research paper formatting.

The main guidelines for formatting a paper in APA Style are as follows:

  • Use a standard font like 12 pt Times New Roman or 11 pt Arial.
  • Set 1 inch page margins.
  • Apply double line spacing.
  • If submitting for publication, insert a APA running head on every page.
  • Indent every new paragraph ½ inch.

Watch the video below for a quick guide to setting up the format in Google Docs.

The image below shows how to format an APA Style title page for a student paper.

APA title page - student version (7th edition)

Running head

If you are submitting a paper for publication, APA requires you to include a running head on each page. The image below shows you how this should be formatted.

APA running head (7th edition)

For student papers, no running head is required unless you have been instructed to include one.

APA provides guidelines for formatting up to five levels of heading within your paper. Level 1 headings are the most general, level 5 the most specific.

APA headings (7th edition)

Reference page

APA Style citation requires (author-date) APA in-text citations throughout the text and an APA Style reference page at the end. The image below shows how the reference page should be formatted.

APA reference page (7th edition)

Note that the format of reference entries is different depending on the source type. You can easily create your citations and reference list using the free APA Citation Generator.

Generate APA citations for free

Prevent plagiarism. Run a free check.

The main guidelines for writing an MLA style paper are as follows:

  • Use an easily readable font like 12 pt Times New Roman.
  • Use title case capitalization for headings .

Check out the video below to see how to set up the format in Google Docs.

On the first page of an MLA paper, a heading appears above your title, featuring some key information:

  • Your full name
  • Your instructor’s or supervisor’s name
  • The course name or number
  • The due date of the assignment

MLA heading

Page header

A header appears at the top of each page in your paper, including your surname and the page number.

MLA page header

Works Cited page

MLA in-text citations appear wherever you refer to a source in your text. The MLA Works Cited page appears at the end of your text, listing all the sources used. It is formatted as shown below.

The format of the MLA Works Cited page

You can easily create your MLA citations and save your Works Cited list with the free MLA Citation Generator.

Generate MLA citations for free

The main guidelines for writing a paper in Chicago style (also known as Turabian style) are:

  • Use a standard font like 12 pt Times New Roman.
  • Use 1 inch margins or larger.
  • Place page numbers in the top right or bottom center.

Format of a Chicago Style paper

Chicago doesn’t require a title page , but if you want to include one, Turabian (based on Chicago) presents some guidelines. Lay out the title page as shown below.

Example of a Chicago Style title page

Bibliography or reference list

Chicago offers two citation styles : author-date citations plus a reference list, or footnote citations plus a bibliography. Choose one style or the other and use it consistently.

The reference list or bibliography appears at the end of the paper. Both styles present this page similarly in terms of formatting, as shown below.

Chicago bibliography

To format a paper in APA Style , follow these guidelines:

  • Use a standard font like 12 pt Times New Roman or 11 pt Arial
  • Set 1 inch page margins
  • Apply double line spacing
  • Include a title page
  • If submitting for publication, insert a running head on every page
  • Indent every new paragraph ½ inch
  • Apply APA heading styles
  • Cite your sources with APA in-text citations
  • List all sources cited on a reference page at the end

The main guidelines for formatting a paper in MLA style are as follows:

  • Use an easily readable font like 12 pt Times New Roman
  • Include a four-line MLA heading on the first page
  • Center the paper’s title
  • Use title case capitalization for headings
  • Cite your sources with MLA in-text citations
  • List all sources cited on a Works Cited page at the end

The main guidelines for formatting a paper in Chicago style are to:

  • Use a standard font like 12 pt Times New Roman
  • Use 1 inch margins or larger
  • Place page numbers in the top right or bottom center
  • Cite your sources with author-date citations or Chicago footnotes
  • Include a bibliography or reference list

To automatically generate accurate Chicago references, you can use Scribbr’s free Chicago reference generator .

Cite this Scribbr article

If you want to cite this source, you can copy and paste the citation or click the “Cite this Scribbr article” button to automatically add the citation to our free Citation Generator.

Caulfield, J. (2023, January 20). Research Paper Format | APA, MLA, & Chicago Templates. Scribbr. Retrieved February 12, 2024, from https://www.scribbr.com/research-paper/research-paper-format/

Is this article helpful?

Jack Caulfield

Jack Caulfield

Other students also liked, apa format for academic papers and essays, mla format for academic papers and essays, chicago style format for papers | requirements & examples, what is your plagiarism score.

Baruch college | Newman Library -->

  • Newman Library
  • Research Guides

ENG 2150: Writing II - Prof. Rios

  • Finding Sources for Your Paper
  • Finding an Argument to Make
  • Citing Sources
  • Getting Help with Your Paper

Understanding Sources

Authority and relevance of sources.

  • Is contextual
  • Depends on your needs

Ways to Use Sources

Scholarly vs. popular sources.

Location of different kinds of sources on continuum

Expertise and authority of an author

  • What do we know about the author?
  • Have they written or spoken about this topic before?
  • Do they teach at college or university on this topic?
  • Are they affiliated with a research institution or agency or think tank?
  • What do other authors think of this one?

What's in OneSearch?

Onesearch on the library home page.

When you click "Define Your Search," you are presented with options you must select before you can type your search terms:

Search options within the search box

Books (print + ebooks) will search the OneSearch system.

Articles will search the OneSearch system for articles in journals, newspapers, and magazines.

Videos will search the OneSearch system for streaming videos and DVDs

Books + Articles + Videos will search OneSearch for all of the above format types and more.

Databases will link you to a page with an A-Z list of all library databases.

Journals will search the OneSearch system for journals we have online and in print.

Newspapers + Magazines will search the OneSearch system for newspapers and magazines we have online and in print.

Course Reserves will link you to a page listing all the courses where we have items on reserve.

Library Services & Policies will search just the library web pages for info about our services.

Top Search Tips

1. Quote marks around phrases = more precise results

quotation marks around phrases

2. Type AND in all caps between concepts

Search connector words in all caps

3. "Filter" your search results by resource type, date, and more. Use the "Limit to" option for "Peer Reviewed Journals" to get just scholarly journal articles.

Filter my results on left side

4. Use "Advanced Search" mode for greater control

Advanced search mode

Identifying Resource Types in Search Results

  • if there's a "PEER REVIEWED" label on that listing, the article came from a scholarly, peer-reviewed journal
  • if there's no label, the article is from a newspaper or magazine
  • If there is a green "Available Online" link in the listing, that's an ebook
  • If there is no green "Available Online link, that's a print book
  • Chapter from an ebook
  • entries from encyclopedias and dictionaries

Search results page in OneSearch

  • << Previous: Finding an Argument to Make
  • Next: Citing Sources >>
  • Last updated: Feb 14, 2024 2:00 PM
  • Skip to Guides Search
  • Skip to breadcrumb
  • Skip to main content
  • Skip to footer
  • Skip to chat link
  • Report accessibility issues and get help
  • Go to Penn Libraries Home
  • Go to Franklin catalog

Critical Writing Seminar: Craft of Prose : Researching the White Paper

  • Getting started
  • News and Opinion Sites
  • Academic Sources
  • Grey Literature
  • Substantive News Sources
  • What to Do When You Are Stuck
  • Understanding a citation
  • Examples of Quotation
  • Examples of Paraphrase
  • Chicago Manual of Style: Citing Images
  • Researching the Op-Ed
  • Researching Prospective Employers
  • Resume Resources
  • Cover Letter Resources

Research the White Paper

Researching the White Paper:

The process of researching and composing a white paper shares some similarities with the kind of research and writing one does for a high school or college research paper. What’s important for writers of white papers to grasp, however, is how much this genre differs from a research paper.  First, the author of a white paper already recognizes that there is a problem to be solved, a decision to be made, and the job of the author is to provide readers with substantive information to help them make some kind of decision--which may include a decision to do more research because major gaps remain. 

Thus, a white paper author would not “brainstorm” a topic. Instead, the white paper author would get busy figuring out how the problem is defined by those who are experiencing it as a problem. Typically that research begins in popular culture--social media, surveys, interviews, newspapers. Once the author has a handle on how the problem is being defined and experienced, its history and its impact, what people in the trenches believe might be the best or worst ways of addressing it, the author then will turn to academic scholarship as well as “grey” literature (more about that later).  Unlike a school research paper, the author does not set out to argue for or against a particular position, and then devote the majority of effort to finding sources to support the selected position.  Instead, the author sets out in good faith to do as much fact-finding as possible, and thus research is likely to present multiple, conflicting, and overlapping perspectives. When people research out of a genuine desire to understand and solve a problem, they listen to every source that may offer helpful information. They will thus have to do much more analysis, synthesis, and sorting of that information, which will often not fall neatly into a “pro” or “con” camp:  Solution A may, for example, solve one part of the problem but exacerbate another part of the problem. Solution C may sound like what everyone wants, but what if it’s built on a set of data that have been criticized by another reliable source?  And so it goes. 

For example, if you are trying to write a white paper on the opioid crisis, you may focus on the value of  providing free, sterilized needles--which do indeed reduce disease, and also provide an opportunity for the health care provider distributing them to offer addiction treatment to the user. However, the free needles are sometimes discarded on the ground, posing a danger to others; or they may be shared; or they may encourage more drug usage. All of those things can be true at once; a reader will want to know about all of these considerations in order to make an informed decision. That is the challenging job of the white paper author.     
 The research you do for your white paper will require that you identify a specific problem, seek popular culture sources to help define the problem, its history, its significance and impact for people affected by it.  You will then delve into academic and grey literature to learn about the way scholars and others with professional expertise answer these same questions. In this way, you will create creating a layered, complex portrait that provides readers with a substantive exploration useful for deliberating and decision-making. You will also likely need to find or create images, including tables, figures, illustrations or photographs, and you will document all of your sources. 

Chinese Studies Librarian

Profile Photo

Connect to a Librarian Live Chat or "Ask a Question"

  • Librarians staff live chat from 9-5 Monday through Friday . You can also text to chat: 215-543-7674
  • You can submit a question 24 hours a day and we aim to respond within 24 hours 
  • You can click the "Schedule Appointment" button above in librarian's profile box (to the left), to schedule a consultation with her in person or by video conference.  
  • You can also make an appointment with a  Librarian by subject specialization . 
  • Connect by email with a subject librarian

Find more easy contacts at our Quick Start Guide

  • Next: Getting started >>
  • Last Updated: Feb 12, 2024 12:03 PM
  • URL: https://guides.library.upenn.edu/WRIT0020-302
  • Skip to main content
  • Keyboard shortcuts for audio player

Shots - Health News

  • Your Health
  • Treatments & Tests
  • Health Inc.
  • Public Health

Reproductive rights in America

Research at the heart of a federal case against the abortion pill has been retracted.

Selena Simmons-Duffin

Selena Simmons-Duffin

how write reference research paper

The Supreme Court will hear the case against the abortion pill mifepristone on March 26. It's part of a two-drug regimen with misoprostol for abortions in the first 10 weeks of pregnancy. Anna Moneymaker/Getty Images hide caption

The Supreme Court will hear the case against the abortion pill mifepristone on March 26. It's part of a two-drug regimen with misoprostol for abortions in the first 10 weeks of pregnancy.

A scientific paper that raised concerns about the safety of the abortion pill mifepristone was retracted by its publisher this week. The study was cited three times by a federal judge who ruled against mifepristone last spring. That case, which could limit access to mifepristone throughout the country, will soon be heard in the Supreme Court.

The now retracted study used Medicaid claims data to track E.R. visits by patients in the month after having an abortion. The study found a much higher rate of complications than similar studies that have examined abortion safety.

Sage, the publisher of the journal, retracted the study on Monday along with two other papers, explaining in a statement that "expert reviewers found that the studies demonstrate a lack of scientific rigor that invalidates or renders unreliable the authors' conclusions."

It also noted that most of the authors on the paper worked for the Charlotte Lozier Institute, the research arm of anti-abortion lobbying group Susan B. Anthony Pro-Life America, and that one of the original peer reviewers had also worked for the Lozier Institute.

The Sage journal, Health Services Research and Managerial Epidemiology , published all three research articles, which are still available online along with the retraction notice. In an email to NPR, a spokesperson for Sage wrote that the process leading to the retractions "was thorough, fair, and careful."

The lead author on the paper, James Studnicki, fiercely defends his work. "Sage is targeting us because we have been successful for a long period of time," he says on a video posted online this week . He asserts that the retraction has "nothing to do with real science and has everything to do with a political assassination of science."

He says that because the study's findings have been cited in legal cases like the one challenging the abortion pill, "we have become visible – people are quoting us. And for that reason, we are dangerous, and for that reason, they want to cancel our work," Studnicki says in the video.

In an email to NPR, a spokesperson for the Charlotte Lozier Institute said that they "will be taking appropriate legal action."

Role in abortion pill legal case

Anti-abortion rights groups, including a group of doctors, sued the federal Food and Drug Administration in 2022 over the approval of mifepristone, which is part of a two-drug regimen used in most medication abortions. The pill has been on the market for over 20 years, and is used in more than half abortions nationally. The FDA stands by its research that finds adverse events from mifepristone are extremely rare.

Judge Matthew Kacsmaryk, the district court judge who initially ruled on the case, pointed to the now-retracted study to support the idea that the anti-abortion rights physicians suing the FDA had the right to do so. "The associations' members have standing because they allege adverse events from chemical abortion drugs can overwhelm the medical system and place 'enormous pressure and stress' on doctors during emergencies and complications," he wrote in his decision, citing Studnicki. He ruled that mifepristone should be pulled from the market nationwide, although his decision never took effect.

how write reference research paper

Matthew Kacsmaryk at his confirmation hearing for the federal bench in 2017. AP hide caption

Matthew Kacsmaryk at his confirmation hearing for the federal bench in 2017.

Kacsmaryk is a Trump appointee who was a vocal abortion opponent before becoming a federal judge.

"I don't think he would view the retraction as delegitimizing the research," says Mary Ziegler , a law professor and expert on the legal history of abortion at U.C. Davis. "There's been so much polarization about what the reality of abortion is on the right that I'm not sure how much a retraction would affect his reasoning."

Ziegler also doubts the retractions will alter much in the Supreme Court case, given its conservative majority. "We've already seen, when it comes to abortion, that the court has a propensity to look at the views of experts that support the results it wants," she says. The decision that overturned Roe v. Wade is an example, she says. "The majority [opinion] relied pretty much exclusively on scholars with some ties to pro-life activism and didn't really cite anybody else even or really even acknowledge that there was a majority scholarly position or even that there was meaningful disagreement on the subject."

In the mifepristone case, "there's a lot of supposition and speculation" in the argument about who has standing to sue, she explains. "There's a probability that people will take mifepristone and then there's a probability that they'll get complications and then there's a probability that they'll get treatment in the E.R. and then there's a probability that they'll encounter physicians with certain objections to mifepristone. So the question is, if this [retraction] knocks out one leg of the stool, does that somehow affect how the court is going to view standing? I imagine not."

It's impossible to know who will win the Supreme Court case, but Ziegler thinks that this retraction probably won't sway the outcome either way. "If the court is skeptical of standing because of all these aforementioned weaknesses, this is just more fuel to that fire," she says. "It's not as if this were an airtight case for standing and this was a potentially game-changing development."

Oral arguments for the case, Alliance for Hippocratic Medicine v. FDA , are scheduled for March 26 at the Supreme Court. A decision is expected by summer. Mifepristone remains available while the legal process continues.

  • Abortion policy
  • abortion pill
  • judge matthew kacsmaryk
  • mifepristone
  • retractions
  • Abortion rights
  • Supreme Court

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • View all journals
  • My Account Login
  • Explore content
  • About the journal
  • Publish with us
  • Sign up for alerts
  • Open access
  • Published: 12 February 2024

A conserved interdomain microbial network underpins cadaver decomposition despite environmental variables

  • Zachary M. Burcham 1 , 2 ,
  • Aeriel D. Belk 1 , 3 ,
  • Bridget B. McGivern   ORCID: orcid.org/0000-0001-9023-0018 4 ,
  • Amina Bouslimani 5 ,
  • Parsa Ghadermazi 6 ,
  • Cameron Martino 7 ,
  • Liat Shenhav 8 , 9 , 10 ,
  • Anru R. Zhang 11 , 12 ,
  • Pixu Shi 11 ,
  • Alexandra Emmons 1 ,
  • Heather L. Deel 13 ,
  • Zhenjiang Zech Xu   ORCID: orcid.org/0000-0003-1080-024X 14 ,
  • Victoria Nieciecki   ORCID: orcid.org/0000-0002-1891-5909 1 , 13 ,
  • Qiyun Zhu   ORCID: orcid.org/0000-0002-3568-6271 7 , 15 , 16 ,
  • Michael Shaffer 4 ,
  • Morgan Panitchpakdi 5 ,
  • Kelly C. Weldon 5 ,
  • Kalen Cantrell   ORCID: orcid.org/0000-0002-6262-1668 17 ,
  • Asa Ben-Hur 18 ,
  • Sasha C. Reed 19 ,
  • Greg C. Humphry 7 ,
  • Gail Ackermann 7 ,
  • Daniel McDonald 7 ,
  • Siu Hung Joshua Chan   ORCID: orcid.org/0000-0002-7707-656X 6 ,
  • Melissa Connor 20 ,
  • Derek Boyd   ORCID: orcid.org/0000-0003-1444-0536 21 , 22 ,
  • Jake Smith 21 , 23 ,
  • Jenna M. S. Watson 21 ,
  • Giovanna Vidoli 21 ,
  • Dawnie Steadman   ORCID: orcid.org/0000-0003-0812-0739 21 ,
  • Aaron M. Lynne 24 ,
  • Sibyl Bucheli 24 ,
  • Pieter C. Dorrestein   ORCID: orcid.org/0000-0002-3003-1030 5 ,
  • Kelly C. Wrighton 4 ,
  • David O. Carter   ORCID: orcid.org/0000-0003-1885-5237 25 ,
  • Rob Knight   ORCID: orcid.org/0000-0002-0975-9019 7 , 17 , 26 , 27 &
  • Jessica L. Metcalf   ORCID: orcid.org/0000-0001-8374-8046 1 , 13 , 28  

Nature Microbiology ( 2024 ) Cite this article

1990 Accesses

1 Citations

353 Altmetric

Metrics details

  • Microbial ecology

Microbial breakdown of organic matter is one of the most important processes on Earth, yet the controls of decomposition are poorly understood. Here we track 36 terrestrial human cadavers in three locations and show that a phylogenetically distinct, interdomain microbial network assembles during decomposition despite selection effects of location, climate and season. We generated a metagenome-assembled genome library from cadaver-associated soils and integrated it with metabolomics data to identify links between taxonomy and function. This universal network of microbial decomposers is characterized by cross-feeding to metabolize labile decomposition products. The key bacterial and fungal decomposers are rare across non-decomposition environments and appear unique to the breakdown of terrestrial decaying flesh, including humans, swine, mice and cattle, with insects as likely important vectors for dispersal. The observed lockstep of microbial interactions further underlies a robust microbial forensic tool with the potential to aid predictions of the time since death.

Decomposition is one of Earth’s most foundational processes, sustaining life through the recycling of dead biological material 1 , 2 . This resource conversion is critical for fuelling core ecosystem functions, such as plant productivity and soil respiration. Microbial networks underpin organic matter breakdown 3 , yet their ecology remains in a black box, obscuring our ability to accurately understand and model ecosystem function, resilience and biogeochemical carbon and nutrient budgets. While DNA-based assessments of decomposer microbial communities have occurred in plant litter 4 , 5 and a few in mammals 6 , 7 , little has been revealed about the microbial ecology of how decomposer microbial communities assemble, interact or function in the ecosystem. Our understanding of how animal remains, or carrion, decompose is in its infancy due to the historical focus on plant litter, which dominates decomposing biomass globally. Nevertheless, an estimated 2 billion metric tons of high-nutrient animal biomass 8 contribute substantially to ecosystem productivity, soil fertility, and a host of other ecosystem functions and attributes 9 , 10 . Carbon and nutrients from carrion biomass can be consumed by invertebrate and vertebrate scavengers, enter the atmosphere as gas, or be metabolized by microbes in situ or via leachate in the surrounding soils 11 , 12 . The proportion of carrion carbon and nutrients entering each resource pool is not well quantified and probably highly variable with substantial contributions to each at an ecosystem scale 2 , 13 . Unlike with plant litter, which is primarily composed of cellulose, animal decomposers must predominantly break down proteins and lipids, which require a vastly different metabolic repertoire. How microbial decomposers assemble to break down these organic compounds is not well understood. For plant litter, it has been proposed that functional redundancy allows different communities of microbes to assemble in any given location 14 and perform similar functions. Alternatively, similar microbial community members, or microbial networks, may assemble across sites to outcompete other community members and thrive on nutrients 15 .

Recent research has demonstrated that microbial community response over the course of terrestrial human cadaver decomposition and across a range of mammals, results in a substantial microbial community change through time that is repeatable across individuals 6 , 7 , 16 , 17 , 18 and appears somewhat similar across different soil types 6 and robust to scavenger activity 16 . These data suggest the potential for universal microbial decomposer networks that assemble in response to mammalian remains. However, it remains unclear how the effects of environmental variability, such as differences in climate, geographic location and season, may affect the assembly processes and interactions of microbial decomposers. Yet understanding and predicting this assembly is important for our understanding of ecosystems and informs practical applications. For example, profiling microbial succession patterns associated with human remains may lead to a novel tool for predicting the postmortem interval (PMI), which has critical societal impact as evidence for death investigations. Within laboratory experiments 6 , 18 , as well as field experiments in single locations 6 , 19 , microbial decomposer community succession is closely linked to PMI at accuracies relevant for forensic applications 6 , 17 , 18 , but these studies do not inform questions of microbial variation across sites, climates and seasons. Consequently, a robust understanding of how microbial ecological patterns of mammalian, and specifically human, decomposition vary is critical for using and improving these important forensic tools. Unlocking the microbial ecology black box for mammal decomposition, or more generally carrion decomposition, could provide actionable knowledge for innovation in agriculture and the human death care industry (for example, composting of bodies) 20 , sustainability (for example, animal mass mortality events) 21 and the forensic sciences (for example, estimating PMI) 22 , as well as guide future research on plant decomposition and maintaining global productivity under anthropogenic change.

To address ecological and forensic research questions on decomposer network assembly and function, we used three willed-body donation anthropological facilities in terrestrial environments across two climate types within the United States (Fig. 1a and Extended Data Fig. 1a,b ) 23 . We asked whether temporal trends in microbial decomposer communities that we previously characterized in a limited experiment using human cadavers at a single geographic location 6 were generalizable across climate, geographic locations and seasons. Over the course of decomposition, we compared the microbial response to decomposition across 36 human bodies within (temperate forest) and between (temperate forest vs semi-arid steppe) climate types. We used multi-omic data (16S and 18S ribosomal (r)RNA gene amplicons, metagenomics and metabolomics) to reveal microbial ecological responses to cadaver decomposition over the first 21 d postmortem (Fig. 1b and Extended Data Fig. 1c ), when decomposition rates are generally fast and dynamic (Fig. 1c , metadata in Supplementary Table 1 ). Here we show that a universal microbial decomposer network assembles despite location, climate and seasonal effects, with evidence of increased metabolic efficiencies to process the ephemeral and abundant lipid- and protein-rich compounds. Key members of the microbial decomposer network are also found associated with swine, cattle and mouse carrion 16 , 24 , 25 , 26 , suggesting that they are not human-specific, but probably general to mammal or animal carrion. Furthermore, the universal microbial network communities underlie a robust microbial-based model for predicting PMI.

figure 1

a , Köppen–Geiger climate map showing ARF and STAFS as ‘temperate without a dry season and hot summer’ and FIRS as ‘arid steppe cold’ adapted from ref. 23 . Thirty-six cadavers in total were placed ( N  = 36), 3 per season for a sum of 12 at each location. b , Upset plot representing the experimental design for the total sample size ( x axis) and number of shared/paired samples ( y axis) for each data type. MetaG, metagenomics; Metab, metabolomics; 18S, 18S rRNA amplicon; 16S, 16S rRNA amplicon. c , Total body score, a visual score of decomposition calculated over the course of decomposition 27 , illustrating how decomposition progresses at each location and by season in triplicate. Dashed lines separate sections of early, active and advanced stages of decomposition as determined by a temperature-based unit of time, accumulated degree day (ADD), calculated by continuously summing the mean daily temperature above 0 °C from left to right. Point transparency increases with days since placement.

Source data

Nutrient-rich cadaver decomposition.

Terrestrial mammalian decomposition is a dynamic process that is partly governed by environmental conditions 1 , 2 . We observed that cadavers placed in the same climate (temperate) decomposed similarly across locations within a season, as determined by a visual total body score (TBS) of decomposition progression (Fig. 1c ) 27 . Cadavers placed in a semi-arid climate (that is, FIRS) generally progressed more slowly through decomposition over the 21 d, which is probably due to decreased temperatures, humidity and precipitation in the semi-arid environment (Extended Data Fig. 1a,b ) 9 , 28 . We observed visual cadaver decomposition progression to be impacted by season, wherein summer was the most consistent across locations (Fig. 1c ). As cadavers and mammalian carrion decompose, they release a complex nutrient pool that impacts the surrounding environment, often resulting in the death and restructuring of nearby plant life 2 , 29 due to generally high inputs of nitrogen 2 , 6 , 9 , 30 , 31 , which is primarily in the form of ammonium 6 , as well as carbon 2 , 6 , 10 , 30 , 31 and phosphorous 9 , 29 . We characterized the cadaver-derived nutrient pool via untargeted metabolomics using liquid chromatography with tandem mass spectrometry (LC–MS/MS) data. Cadaver skin and associated soil metabolite profiles were distinct (Extended Data Fig. 2a,b ). Overall, profiles were largely dominated by likely cadaver-derived lipid-like and protein-like compounds, along with plant-derived lignin-like compounds (Extended Data Fig. 2c,d ). As decomposition progressed, both cadaver-associated soil and skin profiles became enriched in linoleic acids, aleuritic acids, palmitic acids, long-chain fatty acids, fatty amides and general amino acids (Supplementary Tables 2 and 3 ). Furthermore, we estimated a reduction of thermodynamic favourability in the nutrient pool at all locations (Extended Data Fig. 2e,f ), a similar pattern found in the microbial breakdown of plant material in soils 32 . These data suggest that during the first weeks of decomposition, more recalcitrant lipid-like and lipid-derivative nutrients build up within soils as decomposers preferentially utilize labile protein-like resources, but with climate-dependent abundance variations in lipid-like (Extended Data Fig. 2g ) and geographic-dependent variations in protein-like compounds (Extended Data Fig. 2h ). These patterns may also be influenced by the physical properties of soil at each location such as texture, density and stoichiometry.

Cadaver microbial decomposer assembly

The lipid- and protein-rich cadaver nutrient influx is a major ecological disturbance event that attracts scavengers from across the tree of life and initiates the assembly of a specific microbial decomposer community. On the basis of our metabolite data, we hypothesized that soil decomposer microbial communities preferentially shift to efficiently utilize more labile compounds (for example, amino acids from proteins and possibly also carbohydrates such as glycogen, which were not detected via LC–MS/MS metabolomics) and temporarily leave the less-labile compounds (for example, lipids) in the system. By building a metagenome-assembled genome (MAG) database from human decomposition-associated soils (Extended Data Fig. 3a,b and Supplementary Tables 4 – 6 ), we reconstructed genome-scale metabolic models to characterize how potential metabolic efficiencies of soil microbial communities shift in response to three major resources: lipids, amino acids and carbohydrates. Indeed, we found that temperate decomposer metabolic efficiency of labile resources was positively correlated with a temperature-based timeline of decomposition (accumulated degree day (ADD)) (Fig. 2a–c , Extended Data Fig. 3c and Supplementary Tables 7 – 9 ). We found that two MAGs constituted a large portion of the increased amino acid and carbohydrate metabolism efficiencies at temperate locations: Oblitimonas alkaliphila ( Thiopseudomonas alkaliphila ) (Extended Data Fig. 3d ) and Corynebacterium intestinavium (Extended Data Fig. 3e ), respectively. This microbial response is probably an effect of heterogeneous selection (that is, selection driving the community to become different) driving the assemblage of the decomposer community, as heterogeneous selection increases relative to stochastic forces and homogeneous selection during decomposition (Fig. 2d,e , Extended Data Fig. 3f , and Supplementary Tables 10 and 11 ). We further hypothesized that microbe–microbe interactions probably contribute to selection 33 , which we investigated by calculating metabolic competitive and cooperative interaction potentials between our genome-scale metabolic models 34 , 35 . We found that metabolic competition potential initially increased at one temperate and the semi-arid location, suggesting an increase in microbes with similar resource needs (Extended Data Fig. 3g , and Supplementary Tables 12 and 13 ), which was not seen when communities were randomly subsampled within each site and decomposition stage (Extended Data Fig. 3h and Supplementary Table 12 ). Furthermore, we found that communities in temperate climates increased cross-feeding potential (that is, sharing of metabolic products) from early/active to advanced decomposition (Fig. 3a , and Supplementary Tables 12 and 13 ) and had a substantially higher number of cross-feeding exchanges during late decomposition than semi-arid climate communities (Fig. 3b and Supplementary Table 14 ), suggesting the increased potential for metabolic activity. The molecules predicted most for exchange by the models are common by-products of mammalian decomposition 36 , 37 , specifically of protein degradation 38 , and included hydrogen sulfide, acetaldehyde and ammonium, and 56% of the top 25 total exchanged molecules were amino acids. In contrast to temperate locations, semi-arid decomposer communities demonstrated a relatively diminished responsiveness to decomposition stage (Fig. 3c , Extended Data Fig. 4a , and Supplementary Tables 15 and 16 ) and did not significantly shift their metabolism efficiencies (Fig. 2a–c , Extended Data Fig. 3c and Supplementary Tables 7 – 9 ), probably due to a lack of water, which leads to higher metabolic costs 39 , decreased substrate supply 40 and growth 41 . Despite a less measurable microbial response at the semi-arid location, we did detect an increase in cross-feeding potential from early to active decomposition stages, suggesting that the semi-arid community has an increased ability to respond to decomposition nutrients (Fig. 3a , and Supplementary Tables 12 and 13 ) but probably at a smaller scale than temperate locations.

figure 2

a – c , Lipid ( a ), carbohydrate ( b ) and amino acid ( c ) metabolism efficiency as determined by the maximum ATP per C-mol of substrate that can be obtained from each community, plotted against the ADD the community was sampled. ARF n  = 212, STAFS n  = 198 and FIRS n  = 158 biologically independent samples. Data are presented as mean ± 95% confidence interval (CI). Significance was tested with linear mixed-effects models within each location including a random intercept for cadavers with two-tailed ANOVA and no multiple-comparison adjustments. ARF amino acids P  = 6.27 × 10 −23 , STAFS amino acids P  = 6.626 × 10 −10 , STAFS carbohydrate P  = 2.294 × 10 −07 and STAFS lipid P  = 3.591 × 10 −02 . d , Pairwise comparisons to obtain βNTI values focused on successional assembly trends by comparing initial soil at time of cadaver placement to early decomposition soil, then early to active and so on (PL, placement; EA, early; AC, active; AD, advanced) in the 16S rRNA amplicon dataset, showing that strong selection forces are pushing the community to differentiate. ARF n  = 232, STAFS n  = 202 and FIRS n  = 182 biologically independent samples. In boxplots, the lower and upper hinges of the box correspond to the first and third quartiles (the 25th and 75th percentiles); the upper and lower whiskers extend from the hinge to the largest and smallest values no further than 1.5× interquartile range (IQR), respectively; and the centre lines represent the median. The βNTI mean (diamond symbol) change between decomposition stage is represented by connected lines. Dashed lines represent when |βNTI| = 2. A |βNTI| value < 2 indicates stochastic forces (white background) drive community assembly. βNTI values <−2 and >2 indicate homogeneous (blue background) and heterogeneous (yellow background) selection drive assembly, respectively. The width of the violin plot represents the density of the data at different values. Significance was tested with Dunn Kruskal–Wallis H -test, with multiple-comparison P values adjusted using the Benjamini–Hochberg method. e , Representation of heterogeneous selection pressure relative abundance within the total pool of assembly processes increases over decomposition in the 16S rRNA amplicon dataset. Bars were calculated by dividing the number of community comparisons within with βNTI > +2 by the total number of comparisons. * P  < 0.05, ** P  < 0.01 and *** P  < 0.001.

Source Data

figure 3

a , Predicted cross-feeding interactions from MAGs are site-specific and significantly altered over decomposition. ARF n  = 201, STAFS n  = 188 and FIRS n  = 151 biologically independent samples. In boxplots, the lower and upper hinges correspond to the first and third quartiles (the 25th and 75th percentiles); the upper and lower whiskers extend from the hinge to the largest and smallest values no further than 1.5× IQR; the centre lines represent the median. Significance was tested with Dunn Kruskal–Wallis H -test, with multiple-comparison P values adjusted with the Benjamini–Hochberg method. ARF early-active P  = 1.95 × 10 −23 , early-advanced P  = 1.67 × 10 −23 ; STAFS early-active P  = 5.53 × 10 −39 , early-advanced P  = 3.65 × 10 −03 , active-advanced P  = 2.04 × 10 −24 ; FIRS early-active P  = 3.81 × 10 −15 . b , Increased cross-feeding reactions during semi-arid active decomposition and temperate advanced decomposition are summarized to show that compounds such as amino acids (red) are common among the top 25 potential cross-fed molecules from MAGs. c , Phylogenetic turnover in decomposition soil vs control soil shows that temperate climates react quickly to decomposition, while the more arid site does not quickly change (dashed lines represent breaks for early, active (grey shading) and advanced decomposition stages) using the 16S rRNA gene amplicon dataset. ARF n  = 414, STAFS n  = 316 and FIRS n  = 310 biologically independent samples. Data are presented as mean ± 95% CI. Significance was tested using linear mixed-effects models within each location, including a random intercept for cadavers with two-tailed ANOVA and no multiple-comparison adjustments. ARF and STAFS richness P  ≤ 2 × 10 −16 . d , Multi-omic (16S rRNA gene abundances, 18S rRNA gene abundances, MAG abundances, MAG gene abundances, MAG gene functional modules and metabolites) joint-RPCA shows that microbial community ecology is impacted by decomposition stage and geographical location. ** P  < 0.01 and *** P  < 0.001.

We further investigated potential effects of selective environmental conditions via multi-omic, joint robust principal components analysis (joint-RPCA) for dimensionality reduction (see Methods ) 42 , which all (climate, geographic location, season and decomposition stage) significantly shaped the microbial decomposer community ecology (Fig. 3d , Extended Data Fig. 4b–f and Supplementary Table 17 ). Climate (temperate vs semi-arid) along with location (ARF, STAFS, FIRS) significantly shaped the soil microbial community composition (Supplementary Tables 18 – 20 ) and its potential gene function (Supplementary Tables 21 – 22 ). Decomposition soils at temperate sites exhibited strong microbial community phylogenetic turnover (Fig. 3c and Supplementary Table 15 ) and a decrease in microbial richness during decomposition (Extended Data Fig. 4a and Supplementary Table 16 ), while less measurable effects were observed at the semi-arid location (Fig. 3c , Extended Data Fig. 4a , and Supplementary Tables 15 and 16 ). Season appeared to primarily influence soil chemistry as opposed to microbial community composition during decomposition (Supplementary Table 23 ), suggesting possible temperature-associated metabolism changes/limitations of microbial decomposer taxa. Taken together, these data suggest that while stochastic forces play a part in decomposer community assembly, deterministic forces, such as microbial interactions and environmental conditions, also play an important role.

Conserved interdomain soil microbial decomposer network

We discovered a universal network of microbes responding to the cadaver decomposition despite selection effects of climate, location and season on the assembly of the microbial decomposers within the soil. To focus on the universal decomposition effects across locations, we used the joint-RPCA principal component 2 (PC2) scores to generate the universal decomposition network due to their significant change over decomposition stage and reduced impact from location, season and climate (Fig. 4a,b , Extended Data Fig. 4b–f and Supplementary Table 24 ). Therefore, PC2 scores were used to calculate multi-omics of log ratios in late decomposition soil compared to initial and early decomposition soils (Fig. 4c , Extended Data Fig. 4g and Supplementary Table 25 ), which allowed us to identify key co-occurring bacterial and eukaryotic microbial decomposers, bacterial functional pathways and metabolites associated with late decomposition (Fig. 5a , Extended Data Fig. 5 and Supplementary Table 26 ). The organism O. alkaliphila , which is central to the network and a large contributor to the increased amino acid metabolism efficiency at temperate locations (Extended Data Fig. 3d ), may play a key role in terrestrial cadaver decomposition as a controller of labile resource utilization in temperate climates, but little is known about its ecology 43 , 44 , 45 . In addition, most microbial key network decomposers (Fig. 5a ; O. alkaliphila , Ignatzschineria , Wohlfahrtiimonas , Bacteroides , Vagococcus lutrae, Savagea , Acinetobacter rudis and Peptoniphilaceae ) represented unique phylogenetic diversity that was extremely rare or undetected in host-associated or soil microbial communities in American Gut Project (AGP) or Earth Microbiome Project (EMP) data sets (Fig. 5b , Extended Data Fig. 6 , and Supplementary Tables 27 and 28 ). Although the decomposers in the group Bacteroides have previously been assumed to derive from a human gut source 46 , 47 , we find that these are instead probably a specialist group of decomposers distinct from gut-associated Bacteroides (Fig. 5b , Extended Data Fig. 6 , and Supplementary Tables 27 and 28 ). The only strong evidence of key network bacterial decomposers emerging from soil and host-associated environments were in the genera Acinetobacter and Peptoniphilus (Fig. 5b , Extended Data Fig. 6 , and Supplementary Tables 27 and 28 ). We more comprehensively characterized microbial decomposer phylogenetic uniqueness with MAG data, which span previously undescribed bacterial orders, families, genera and species (Extended Data Fig. 3a ). Overall, we find that the soil microbial decomposer network is phylogenetically unique and in extremely low relative abundance in the environment until the cadaver nutrient pool becomes available.

figure 4

a , b , Principal component values show that ( a ) facility variation is primarily explained by principal component 3 (PC3) (that is, least overlap between group scores), while variation caused by ( b ) decomposition stage is explained by PC2. c , Change in log ratio of PC scores within omics datasets (metabolites, MAG abundances, 18S rRNA gene abundances and MAG gene functional modules) from initial soil through advanced decomposition stage soil highlights that decomposition stage progression corresponds to compositional shifts. All data types used the same n  = 374 biologically independent samples. Data are presented as mean ± 95% CI.

figure 5

a , Top 20% correlation values from features responsible for the universal late decomposition log-ratio signal in joint-RPCA PC2 visualized in a co-occurrence network. b , Phylogenetic tree representing ASVs associated with key decomposer nodes from the network placed along the top 50 most abundant ASVs taken from AGP gut, AGP skin, EMP soil and EMP host-associated datasets demonstrates that key decomposers are largely phylogenetically unique. Colour represents taxonomic order (full legend in Extended Data Fig. 6 ); the innermost ring represents decomposer placement, while outer rings represent AGP and EMP ASVs, for which bar height represents ASV rank abundance within each environment. A lack of bars indicates that the ASV was not present within the entire dataset. AGP and EMP ASVs were ranked according to the number of samples they were found in each environment. Decomposer ASVs are numbered clockwise (full taxonomy available in Supplementary Table 27 ).

We hypothesized that specialist decomposer network taxa probably interact to metabolize the nutrient pool, which we explored via estimated cross-feeding capabilities of co-occurring communities. Highlighting the importance of these key taxa, microbial decomposer network members accounted for almost half (42.8%) of predicted late decomposition nutrient exchanges (Figs. 3b and 5a , and Supplementary Table 29 ) with Gammaproteobacteria being prominent as both metabolite donors and receivers. For example, O. alkaliphila has the capability to cross-feed with Ignatzschineria , Acinetobacter , Savagea and Vagococcus lutrae , to which it donates amino acids known to be associated with mammalian decomposition such as aspartate, isoleucine, leucine, tryptophan and valine, along with the lipid metabolism intermediate, sn -Glycero-3-phosphoethanolamine 36 (Supplementary Table 30 ). As a receiver, O. alkaliphilia is predicted to receive essential ferrous ions (Fe 2+ ) from Acinetobacter , Savagea and Vagoccocus along with glutamate, proline and lysine from Ignatzschineria . Further, putrescine, a foul-smelling compound produced during decomposition by the decarboxylation of ornithine and arginine, and arginine/ornithine transport systems were universal functions within our network (Fig. 5a ). Cross-feeding analysis identified multiple potential ornithine and/or arginine exchangers, such as Ignatzschineria , Savagea , Wohlfahrtiimonas and O. alkaliphilia (Supplementary Table 31 ). Putrescine is an interdomain communication molecule probably playing an important role in assembling the universal microbial decomposer network by signalling scavengers such as blow flies 48 , which disperse decomposer microbes, as well as directly signalling other key microbial decomposers, such as fungi 49 , 50 , 51 .

Fungi play an essential role in the breakdown of organic matter; however, their processes and interdomain interactions during cadaver decomposition remain underexplored. Our network analysis identified multiple fungal members that are co-occurring with bacteria, belonging to the Ascomycota phylum (Fig. 5a )—a phylum known for its role in breaking down organic matter 6 , 44 , 52 , 53 . In particular, Yarrowia and Candida are known for their ability to utilize lipids, proteins and carbohydrates 44 , 53 , and both have one of their highest correlations with O. alkaliphila (Fig. 5a and Supplementary Table 25 ). The ability of Yarrowia and Candida to break down lipids and proteins during decomposition may serve as interdomain trophic interactions that allow O. alkaliphila to utilize these resources 44 . For example, Yarrowia and Candida genomes contain biosynthesis capabilities for arginine and ornithine that, if excreted, could be taken up by O. alkaliphilia . The complete genome of O. alkaliphilia (Genbank accession no. CP012358 ) contains the enzyme ornithine decarboxylase, which is responsible for converting ornithine to the key compound putrescine 43 .

Machine learning reveals a predictable microbial decomposer ecology

The assembly of a universal microbial decomposer network suggests the potential to build a robust forensics tool. We demonstrate that the PMI (calculated as ADD) can be accurately predicted directly from microbiome-normalized abundance patterns via random forest regression models (Fig. 6a ). High-resolution taxonomic community structure was the best predictor of PMI (Fig. 6b ), particularly normalized abundances of the 16S rRNA gene at the SILVA database level-7 taxonomic rank (L7) of the skin decomposer microbes (Fig. 6a–c ). Interestingly, 3 out of 4 of the skin-associated decomposer taxa that were most informative for the PMI model had similar normalized abundance trends over decompositions for bodies at all locations, suggesting that skin decomposers are more ubiquitous across climates than soil decomposers (Fig. 6d and Extended Data Fig. 7 ). We hypothesize that this is due to the human skin microbiome being more conserved between individuals than the soil microbiome is between geographic locations 54 . In fact, both skin and soil 16S rRNA-based models had the same top taxon as the most important predictor, Helcococcus seattlensis (Fig. 6d and Extended Data Fig. 7 ). H. seattlensis is a member of the order Tissierellales and family Peptoniphilaceae, both of which were key nodes within the universal decomposer network. In line with our hypothesis, H. seattlensis on the skin showed more-similar abundance trends for cadavers decomposing across both climate types, while H. seattlensis trends in the soil were primarily measurable at temperate locations (Fig. 6e and Extended Data Fig. 8 ). We found that normalized abundances of important soil taxa previously established to be in our universal decomposer network had strong climate signals, further suggesting a diminished responsiveness in semi-arid climates, such as temperate-climate responses with H. seattlensis , O. alkaliphila , Savagea sp., Peptoniphilus stercorisuis , Ignatzschineria sp. and Acinetobacter sp. (Extended Data Fig. 8c,d ). However, we found that the three most important PMI model soil taxa, Peptostreptococcus sp., Sporosarcina sp. and Clostridiales Family XI sp., had increased detection with decomposition in both semi-arid and temperate climates (Extended Data Fig. 8c,d ), suggesting that while strong climate-dependent fluctuations exist, there are microbial members that respond more ubiquitously to decomposition independent of climate. In addition, microbiome-based models and a TBS-based model had comparable average mean absolute errors (MAE) (Extended Data Fig. 9a ); however, 16S rRNA microbiome-based model predictions were on average closer to the actual observed values (that is, smaller average residual values), suggesting a higher accuracy (Fig. 6c and Extended Data Fig. 9a ). Lastly, we confirmed the model accuracy and reliability of PMI prediction using 16S rRNA amplicon data with an independent test set of samples that were collected at a different time from cadavers at locations and climates not represented in our model. We discovered that we could accurately predict the true PMIs of samples better than samples with randomized PMIs at all independent test set locations (Extended Data Fig. 9b,c and Supplementary Table 32 ), confirming the generalizability and robustness of our models in predicting new data from multiple geographies and climates with an accuracy useful for forensic death investigations.

figure 6

a , Cross-validation errors of multi-omic data sets. 16S and 18S rRNA gene data were collapsed to SILVA taxonomic level 7 (L7) and 12 (L12). Boxplots represent average prediction MAE in ADD of individual bodies during nested cross-validation of 36 body dataset. 16S rRNA soil face, soil hip, skin face and skin hip datasets contain n  = 600, 616, 588 and 500 biologically independent samples, respectively. 18S rRNA soil face, soil hip, skin face and skin hip datasets contain n  = 939, 944, 837 and 871 biologically independent samples, respectively. Paired 16S rRNA+18S rRNA soil face, soil hip, skin face and skin hip datasets contain n  = 440, 450, 428 and 356 biologically independent samples, respectively. MAG datasets contain n  = 569 biologically independent samples. Metabolite soil hip and skin hip datasets contain n  = 746 and 748 biologically independent samples, respectively. b , Mean absolute prediction errors are lowest when high-resolution taxonomic data are used for model training and prediction. Data represented contain the same biologically independent samples as in a . In boxplots in a and b , the lower and upper hinges of the boxplot correspond to the first and third quartiles (the 25th and 75th percentiles); the upper and lower whiskers extend from the hinge to the largest and smallest values no further than 1.5× IQR; the centre lines represent the median; the diamond symbol represents the mean. c , Linear regressions of predicted to true ADDs to assess model prediction accuracy show that all sampling locations significantly predict ADD. Data represented contain the same biologically independent samples as in a . Data are presented as mean ± 95% CI. Black dashed lines represent ratio of predicted to real ADD predictions at 1:1. The coloured solid lines represent the linear model calculated from the difference between the predicted and real ADD. d , The most important SILVA L7 taxa driving model accuracy from the best-performing model derived from 16S rRNA gene amplicon data sampled from the skin of the face. e , Comparison of abundance changes of the top important taxon, Helcococcus seattlensis , in skin reveals that low-abundance taxa provide predictive responses. Data plotted with loess regression and represent the same biologically independent samples as in a . Data are presented as mean ± 95% CI. Bact., bacterial; Avg., average; Marg., marginal.

We provide a genome-resolved, comprehensive view of microbial dynamics during cadaver decomposition and shed light on the assembly, interactions and metabolic shifts of a universal microbial decomposer network. We found that initial decomposer community assembly is driven by stochasticity, but deterministic forces increase over the course of decomposition, a finding in agreement with other conceptual models of microbial ecology 33 , 55 , 56 , 57 . These processes led to a decomposer network consisting of phylogenetically unique taxa emerging, regardless of season, location and climate, to synergistically break down organic matter. The ubiquitous decomposer and functional network revealed by our multi-omic data suggests that metabolism is coupled to taxonomy, at least to some extent, for cadaver decomposition ecology. However, the overall composition of microbial decomposer communities did vary between different climates and locations, indicating that some functional redundancy also probably exists. In a study of agricultural crop organic matter decomposition (straw and nutrient amendments), researchers similarly demonstrated that although functional redundancy probably plays a role, key microbial taxa emerge as important plant decomposers 15 , and a meta-analysis of microbial community structure–function relationships in plant litter decay found that community composition had a large effect on mass loss 58 . In terms of climatic controls over cadaver decomposition, temperate locations had a more measurable microbial response (for example, phylogenetic turnover, potential cross-feeding) in soils than the arid location in our study, and plant studies support the idea that climate is a strong determinant of decomposition rates and microbial activity 59 .

Despite the lesser response in the arid location, cadaver decomposer microbial ecologies were similar, suggesting that while climate may act as a strong control, microbial community composition follows similar assembly paths. We find evidence that key interdomain microbial decomposers of cadavers (that is, fungi and bacteria) emerge in diverse environments and probably utilize resource partitioning and cross-feeding to break down a nutrient pulse that is rich in lipids, proteins and carbohydrates. This process would be consistent with dogma within leaf litter ecology that fungal decomposers are typically specialized decomposers of complex substrates while bacteria serve as generalists that decompose a broader nutritional landscape 60 . Thus, we hypothesize that fungi (such as Yarrowia and Candida ) assist in the catabolism of complex, dead organic matter (such as lipids and proteins) into simpler compounds (such as fatty acids and amino acids), which are utilized by bacterial community members, (such as O. alkaliphila ) capable of efficiently metabolizing these by-products. This division of labour coupled with microbial interactions drives the assembly of the microbial decomposer community, in a process reminiscent of ecological dynamics observed in leaf litter decomposition 60 .

We suspect that key network microbial decomposers are probably not specific to decomposition of human cadavers and are, in part, maintained or seeded by insects. Key cadaver bacterial decomposers O. alkaliphila , Ignatzschineria , Wohlfahrtiimonas , Bacteroides , Vagococcus lutrae , Savagea , Acinetobacter rudis and Peptoniphilaceae have been detected in terrestrial decomposition studies of swine, cattle and mice (Supplementary Table 33 ) 16 , 24 , 25 , 26 , and a subset detected in aquatic decomposition 61 . Most key network bacterial decomposers, including the well-known blow fly-associated genera Ignatzschineria and Wohlfahrtiimonas 62 , were rare or not detected in a lab-based mouse decomposition study 6 in which insects were excluded (Supplementary Table 33 ). However, a different lab-based study that excluded blow flies but included carrion beetles 26 detected a subset of these key microbial decomposers, suggesting a role for microbe–insect interactions and dispersal by insects 26 , 48 , 63 . Further evidence implicating insects as important vectors is that all key network bacterial decomposers presented here have been detected on blow flies (Supplementary Table 28 ) 6 , 64 . Furthermore, Ascomycota fungal members, such as Yarrowia and Candida , have been previously detected in association with human, swine and mouse remains 6 , 26 , 44 , 53 . Yarrowia can be vertically transmitted from parent to offspring of carrion beetle 63 and may facilitate beetle consumption of carrion. Taken together, these findings suggest that key microbial decomposer taxa identified in this study of human cadavers are probably more generalizable carrion decomposers and are likely inoculated, at least partly, by insects.

We demonstrate the potential practical application of microbiome tools in forensic science by leveraging microbial community succession patterns and machine learning techniques for accurately predicting PMI. Importantly, the predictive models showcase their generalizability by accurately predicting the PMIs of independent test samples collected from various geographic locations and climates, including for test samples collected from a climate region not represented in the training set of the model. The best-performing model was able to accurately predict PMI within ~±3 calendar days during internal validation and on an independent test set (Supplementary Tables 34 and 35 ), which is a useful timeframe for forensic sciences, enabling investigators to establish crucial timelines and aiding in criminal investigations. Prediction errors are probably due to intrinsic (for example, BMI/total mass) 19 , 24 , 65 and/or extrinsic (for example, scavengers, precipitation) 19 , 26 factors not accounted for in the model, but should be a future area of research for model improvement. For example, total mass has been previously shown not to affect microbial decomposer composition in swine 24 ; however, ref. 19 found that Gammaproteobacteria relative abundance correlated with BMI of humans. Within our study, in which cadavers had highly variable initial total masses (Supplementary Table 1 ), Acinetobacter and Ignatzschineria (within Gammaproteobacteria) were important features in our PMI models, suggesting that it is probably robust to BMI (Extended Data Fig. 7 ). In addition, scavenging by invertebrates and vertebrates is another factor that can affect not only the decomposer microbial composition (for example, carrion beetles) 26 but also the microbes themselves which can shape the scavenger community via volatile organic compounds (for example, repel vertebrates but attract insects 48 , 66 ). A better understanding of which intrinsic and extrinsic factors directly affect microbes that are important features for predicting PMI will be an important next step.

Our improved understanding of the microbial ecology of decomposing human cadavers and its more general implications for the crucial and rarely studied carrion nutrient pool is critical for revising concepts of what should be included in carbon and nutrient budgets and the models used to forecast ecosystem function and change 11 . New insight on the role of carrion decomposition in fuelling carbon and nutrient cycling is needed for conceptual and numerical models of biogeochemical cycles and trophic processes 11 ; this study informs how the assembly and interactions among decomposer microbial communities facilitate the turnover and exchange of resources, and begins unlocking one of the remaining black boxes of ecosystem ecology. Finally, these findings may contribute to society by providing potential for a new forensic tool and for potentially modulating decomposition processes in both agricultural and human death industries via the key microbial decomposers identified here.

Site and donor selection

Outdoor experiments on 36 human cadavers were conducted at three willed-body donation facilities: Colorado Mesa University Forensic Investigation Research Station (FIRS), Sam Houston State University Southeast Texas Applied Forensic Science (STAFS) Facility and University of Tennessee Anthropology Research Facility (ARF). Before the start of the project, a meeting was held at STAFS to demonstrate, discuss and agree on sampling protocols. The Institutional Review Board and the Protection of Human Subjects Committee either determined that review was not required or granted exempt status for donors at each respective facility since the proposed research does not involve human donors as defined by federal regulations. Three deceased human donors were placed supine and unclothed on the soil surface in the spring, summer, fall and winter over the years 2016 and 2017 at each facility ( N  = 36). Bodies were placed on soil with no known previous human decomposition. Before placement, STAFS performed minimal removal of vegetation including raking of leaves and removal of shrubbery, and bodies placed at STAFS were placed in cages made of 1 cm × 1 cm wire fences and wooden frames to prevent vertebrate scavenging. The ARF and FIRS did not remove vegetation or place bodies under cages as standard protocol. Furthermore, bodies were placed no closer than 2.5 m between sternum midpoints. Collection date for each donor can be found in the sample metadata, in addition to cause of death if known, initial condition, autopsy status, weight before placement, age in years if known, estimated age if not known, sex, donor storage type, days donor was stored, time since death to cooling and placement head direction (Supplementary Table 1 ). Donor weight was taken at time of intake at ARF and FIRS but is a self-reported measure either by the donor before death or a family member at STAFS. During daily sampling, daily ambient average temperature and humidity, TBS 27 , scavenging status and insect status were recorded if available or applicable. Human bodies were fully exposed to all weather elements and invertebrate scavengers. Inclusion criteria for the remains were specified before the start of the experiment and required that the remains were in the fresh stage of decomposition and had not been frozen (and not extensively cooled) or autopsied before placement at the facility.

Decomposition metric calculations

The Köppen–Geiger climate classification system characterizes both the ARF and STAFS facilities as temperate without a dry season and hot summer (Cfa) and the FIRS facility as a cold semi-arid steppe (BSk) 23 . Average daily temperatures were collected from the National Centers for Environmental Information (NCEI) website ( https://www.ncei.noaa.gov/ ) and monthly total precipitation accumulation over the course of the study was collected from the Weather Underground website ( https://www.wunderground.com/ ) from local weather stations: Grand Junction Regional Airport Station, McGhee Tyson Airport Station and Easterwood Airport Station. Reference 27 TBS quantifies the degree to which decomposition has occurred in three main areas (head, trunk and limbs) 27 . The user assigned values to represent the progress of decomposition on the basis of visual assessment of the cadaver and added these values to generate a TBS at the time of sampling. A maximum score was assigned for each area when the cadaver has reached dry skeletal remains. ADD was estimated using the weather data provided by the NCEI. Degree day on the day of placement was not included, and a base temperature of 0 °C was used. ADD was calculated by adding together all average daily temperatures above 0 °C for all previous days of decomposition, as in ref. 27 , and subtracting the base temperature of 0 °C.

Sample collection and DNA extraction

We sampled the skin surface of the head and torso near the hip along with gravesoils (soils associated with decomposition) associated with each skin site over 21 d of decomposition. Control soil samples were taken of the same soil series and horizon that are not associated with body decomposition (known past or present) from areas within or just outside each facility. We collected swabs of 756 non-decomposition soil (controls), 756 gravesoil near the hip, 756 gravesoil near the face, 756 hip skin and 756 face skin samples ( N  = 3,780). All site samples (skin surface, gravesoil and control soil) were taken using sterile dual-tipped BD SWUBE applicator (REF 281130) swabs as described in ref. 18 , and immediately frozen after each sampling event and kept frozen at −20 °C. Samples were shipped to CU Boulder or Colorado State University overnight on dry ice and immediately stored at −20 °C upon arrival and until DNA extraction. Skin and soil DNA was extracted from a single tip of the dual-tipped swabs using the PowerSoil DNA isolation kit 96-htp (MoBio Laboratories), according to standard EMP protocols ( http://www.earthmicrobiome.org/ ).

Amplicon library preparation and sequencing

Bacterial and archaeal communities were characterized using 16S rRNA gene regions while eukaryotic communities were characterized using 18S rRNA gene regions as universal markers, for all successful skin and soil DNA extracts ( n  = 3,547). To survey bacteria and archaea, we used the primer set 515f (5′GTGYCAGCMGCCGCGGTAA) and 806rb (5′GGACTACNVGGGTWTCTAAT) that targets these domains near-universally 67 , 68 , with barcoded primers allowing for multiplexing, following EMP protocols 69 . To survey microbial eukaryotes, we sequenced a subregion of the 18S rRNA gene using the primers 1391f_illumina (5′GTACACACCGCCCGTC) and EukBr_illumina (5′TGATCCTTCTGCAGGTTCACCTAC) targeting the 3′ end of the 18S rRNA gene. 18S rRNA gene primers were adapted from ref. 70 and target a broad range of eukaryotic lineages. We have successfully generated and analysed data using these gene markers previously 6 , 18 . Primers included error-corrected Golay barcodes to allow for multiplexing while preventing misassignment. PCR amplicons were quantified using Picogreen Quant-iT (Invitrogen, Life Technologies) and pooled from each sample to equimolar ratio in a single tube before shipping to the UC San Diego genomics laboratory for sequencing. For both amplicon types, pools were purified using the UltraClean PCR clean-up kit (Qiagen). 16S rRNA pools were sequenced using a 300-cycle kit on the Illumina MiSeq sequencing platform and 18S rRNA gene pools were sequenced using a 300-cycle kit on the Illumina HiSeq 2500 sequencing platform (Illumina). Samples within a sample type (skin vs soil) were randomly assigned to a sequencing run to prevent potential batch effects. Blank DNA extraction and PCR negative controls were included throughout the entire process from DNA extraction to PCR amplification to monitor contamination ( n  = 592 negative controls).

Shotgun metagenomic library preparation and sequencing

Extracted DNA from a subset of hip-associated soil samples ( n  = 756), soil controls ( n  = 9), blank controls ( n  = 102) and no-template PCR controls ( n  = 15) were chosen to undergo shallow shotgun sequencing to provide in-depth investigation of microbial dynamics within decomposition soil (Supplementary Table 4 ). Our standard protocol followed that of ref. 71 and was optimized for an input quantity of 1 ng DNA per reaction. Before library preparation, input DNA was transferred to 384-well plates and quantified using a PicoGreen fluorescence assay (ThermoFisher). Input DNA was then normalized to 1 ng in a volume of 3.5 μl of molecular-grade water using an Echo 550 acoustic liquid-handling robot (Labcyte). Enzyme mixes for fragmentation, end repair and A-tailing, ligation and PCR were prepared and added at 1:8 scale volume using a Mosquito HV micropipetting robot (TTP Labtech). Fragmentation was performed at 37 °C for 20 min, followed by end repair and A-tailing at 65 °C for 30 min. Sequencing adapters and barcode indices were added in two steps, following the iTru adapter protocol 72 . Universal adapter ‘stub’ adapter molecules and ligase mix were first added to the end-repaired DNA using the Mosquito HV robot and ligation performed at 20 °C for 1 h. Unligated adapters and adapter dimers were then removed using AMPure XP magnetic beads and a BlueCat purification robot (BlueCat Bio). A 7.5 μl magnetic bead solution was added to the total adapter-ligated sample volume, washed twice with 70% ethanol and then resuspended in 7 μl molecular-grade water.

Next, individual i7 and i5 indices were added to the adapter-ligated samples using the Echo 550 robot. Because this liquid handler individually addresses wells and we used the full set of 384 unique error-correcting i7 and i5 indices, we generated each plate of 384 libraries without repeating any barcodes, eliminating the problem of sequence misassignment due to barcode swapping (61, 62). To ensure that libraries generated on different plates could be pooled if necessary and to safeguard against the possibility of contamination due to sample carryover between runs, we also iterated the assignment of i7 to i5 indices per run, such that each unique i7:i5 index combination is only repeated once every 147,456 libraries 72 . A volume of 4.5 μl of eluted bead-washed ligated samples was added to 5.5 μl of PCR master mix and PCR-amplified for 15 cycles. The amplified and indexed libraries were then purified again using AMPure XP magnetic beads and the BlueCat robot, resuspended in 10 μl of water and 9 μl of final purified library transferred to a 384-well plate using the Mosquito HTS liquid-handling robot for library quantitation, sequencing and storage. All samples were then normalized on the basis of a PicoGreen fluorescence assay for sequencing.

Samples were originally sequenced on an Illumina HiSeq 4000; however, due to some sequencing failures, samples were resequenced on the Illumina NovaSeq 6000 platform. To ensure that we obtained the best sequencing results possible, we assessed both sequencing runs and added the best-performing sample of the two runs to the final analysis (that is, if sample X provided more reads from the HiSeq run than the NovaSeq run, we added the HiSeq data from that sample to the final analysis and vice versa). Samples were visually assessed to ensure that no batch effects from the two sequencing runs were present in beta diversity analysis. A list of which samples were pulled from the HiSeq vs NovaSeq runs can be found in the sample metadata under the column ‘best_MetaG_run’, with their corresponding read count under ‘MetaG_read_count’ (Supplementary Table 1 ). In total, 762 samples were sequenced, with 25 coming from the HiSeq run and 737 samples coming from the Novaseq run. Raw metagenomic data had adapters removed and were quality filtered using Atropos (v.1.1.24) 73 with cut-offs of q  = 15 and minimum length of 100 nt. All human sequence data were filtered out by aligning against the Genome Reference Consortium Human Build 38 patch release 7 (GRCh37/hg19) reference database released in 21 March 2016 (ncbi.nlm.nih.gov/assembly/GCF_000001405.13/) and removing all data that matched the reference from the sequence data. Alignment was performed with bowtie2 (v.2.2.3) 74 using the --very-sensitive parameter, and the resulting SAM files were converted to FASTQ format with samtools (v.1.3.1) 75 and bedtools (v.2.26.0) 76 . Metagenomic samples were removed from the analysis if they had <500 k reads. Final metagenomic sample numbers were 569 hip-adjacent soil, 5 soil controls, 102 blank controls and 15 no-template controls.

Metabolite extraction and LC–MS/MS data generation

To investigate the metabolite pools associated with decomposition skin and gravesoils, we performed metabolite extraction on the second tip of the dual-tipped swabs collected from the skin and soil associated with the hip sampling location to ensure all datasets are paired. Skin and soil swab samples were extracted using a solution of 80% methanol. Briefly (with all steps performed on ice), swabs were placed into a pre-labelled 96-well DeepWell plate where A1–D1 were used for a solvent blank and E1–H1 were used for blank clean swabs with extraction solvent added. Swab shafts were cut aseptically and 500 μl of solvent (80% methanol with 0.5 μM sulfamethazine) was added. The DeepWell plate was covered and vortexed for 2 min, followed by 15 min in a water sonication bath. Next, samples were incubated at 4 °C for 2 h, followed by a 12 h incubation at −20 °C. Swab tips were then removed from the solvent and samples were lyophilised. Untargeted metabolomics LC–MS/MS data were generated from each sample. Two types of dataset were generated from each sample: MS1 data for global and statistical analysis and MS/MS data for molecular annotation. Molecular annotation was performed through the GNPS platform https://gnps.ucsd.edu/ . Molecules were annotated with the GNPS reference libraries 77 using accurate parent mass and MS/MS fragmentation pattern according to level 2 or 3 of annotation defined by the 2007 metabolomics standards initiative 78 . If needed and if the authentic chemical standard was available, MS/MS data were collected from the chemical standard and compared to MS/MS spectra of the molecule annotated from the sample (level 1 of annotation).

Amplicon data processing

After data generation, amplicon sequence data were analysed in the Metcalf lab at Colorado State University using the QIIME2 analysis platform v.2020.2 and v.2020.8 (ref. 79 ). In total, 4,139 samples were sequenced, including 592 DNA extraction blank negative and no-template PCR controls. Sequencing resulted in a total of 89,288,561 16S rRNA partial gene reads and 1,543,472,127 18S rRNA partial gene reads. Sequences were quality filtered and demultiplexed using the pre-assigned Golay barcodes. Reads were 150 bp in length. 18S rRNA gene sequences had primers (5′GTAGGTGAACCTGCAGAAGGATCA) removed using cutadapt to ensure that the variable length of the 18S region was processed without primer contamination. Sequences were then classified into amplicon sequence variants (ASVs) in groups of samples that were included on the same sequencing run so the programme could accurately apply the potential error rates from the machine using the Deblur denoising method (v.2020.8.0) 80 . Feature tables and representative sequences obtained from denoising each sequencing run were then merged to create a complete dataset for each amplicon method. Taxonomic identifiers were assigned to the ASVs using the QIIME feature-classifier classify-sklearn method 81 . For the 16S rRNA gene data, these assignments were made using the SILVA 132 99% classifier for the 515fb/806rb gene sequences. ASVs that were assigned to chloroplast or mitochondria (non-microbial sequences) were filtered out of the dataset before continuing analysis. For 18S rRNA data, the RESCRIPt (v.2022.8.0) plugin was used to extract the full 12-level taxonomy from sequences matching the primers from the SILVA 138 99% database, to dereplicate the extracted sequences and to train a classifier to assign labels to ASVs in the feature table 82 . This taxonomy was used to filter out any ASVs that were assigned to Archaea, Streptophyta, Bacteria, Archaeplastida, Arthropoda, Chordata, Mollusca and Mammalia, as well as those that were unassigned, resulting in 5,535 ASVs at a total frequency of 772,483,701. DNA extraction negative and no-template PCR control samples were analysed to determine that contamination within the samples was minimal. Most control samples were low abundance and below the threshold used for rarefaction. The few controls that were above the rarefaction threshold clustered distantly and separately from true samples on principal coordinate analysis (PCoA) and had low alpha diversities, hence samples above the rarefaction depth were considered minimally contaminated and acceptable for analyses. Subsequently, DNA extraction negative and no-template PCR control samples were removed from the dataset and future analyses.

Microbial diversity metrics were generated from both amplicon types using the QIIME2 phylogenetic diversity plugin. The phylogenetic trees were constructed for each amplicon type individually using the fragment-insertion SEPP method 83 against the SILVA 128 99% reference tree. Alpha diversity metrics were calculated using the number of observed features as ASV richness and Faith’s phylogenetic diversity formulas. Statistical comparisons were made using the pairwise Kruskal–Wallis H -test with a Benjamini–Hochberg multiple-testing correction at an alpha level of 0.05 (ref. 84 ). To evaluate beta diversity, the generalized UniFrac method weighted at 0.5 was used to calculate dissimilarity 85 . Statistical comparisons were made using permutational analysis of variance (PERMANOVA) with a multiple-testing correction and an alpha level of 0.05 (ref. 86 ). Taxonomy and alpha diversity visualizations were created using ggplot2 and the viridis package in R 87 , 88 . Beta diversity principal coordinates plots were constructed using the Emperor (v.2022.8.0) plugin in QIIME2 (ref. 89 ). Linear mixed-effects models were used to evaluate the contribution of covariates to a single dependent variable and to test whether community alpha diversity metrics (for example, ASV richness) and beta diversity distances (for example, UniFrac distances) were impacted by decomposition time (that is, ADD) and sampling location (that is, decomposition soil adjacent to the hip and control soil). The response variables were statistically assessed over ADD with sampling site (that is, decomposition soil vs control soil) as an independent variable (fixed effect) and a random intercept for individual bodies to account for repeated measures using the formula: diversity metric ≈ ADD × sampling site + (1|body ID).

Detection of key decomposers in other decomposition studies

16S rRNA gene amplicon sequence data files from refs. 6 , 24 , 25 , 64 , 69 , 90 , 91 were obtained from QIITA 92 under study IDs 10141–10143, 1609, 13114, 10317, 13301 and 11204, respectively. Data obtained from QIITA 92 had been previously demultiplexed and denoised using Deblur 80 and are available on the QIITA 92 study page. Data from ref. 16 were obtained from the NCBI Sequence Read Archive under BioProject PRJNA525153 . Forward reads were imported into QIIME2 (v.2023.5) 79 , demultiplexed and denoised using Deblur (v.1.1.1) 80 . Data from ref. 26 were obtained from the Max Planck Society Edmond repository ( https://edmond.mpdl.mpg.de/dataset.xhtml?persistentId=doi:10.17617/3.UV4FBN ). Forward reads were imported into QIIME2 (v.2023.5) 79 and demultiplexed. Primers (5′ GTGCCAGCMGCCGCGGTAA) were removed using cutadapt (v.4.4) 93 and the data were denoised using Deblur (v.1.1.1) 80 . ASVs from all studies were assigned taxonomy using a naïve Bayes taxonomy classifier trained on the V4 (515f/806r) region of SILVA 138 99% operational taxonomic units (OTUs). Data tables were imported into Jupyter notebooks (Jupyter Lab v.4.0.5) 94 for further analysis (Python v.3.8.16). A search for the 35 universal PMI decomposer ASVs was conducted within each dataset. This search matched exact ASVs in our dataset to other datasets but did not match similar ASVs that may be classified as the same taxon. The relative abundance of each decomposer ASV was first averaged across all samples within a specific metadata category. The average relative abundances were then summed across each decomposer genus. Prevalence tables were constructed by summing the number of samples across a specific metadata category in which each universal decomposer ASV was present. The presence of Wohlfahrtiimonas was found in the ref. 26 dataset; however, these ASVs were not exact sequence matches to our universal Wohlfahrtiimonas decomposers and probably represent insect-associated strains (Supplementary Table 33 ; Wohlfahrtiimonadaceae column). We searched within the remaining studies for the presence of other ASVs assigned to the Wohlfahrtiimonas genus or ASVs that were assigned to the Wohlfahrtiimonadaceae family but these were unidentified at the genus level. Average relative abundances were calculated as described above.

Community assembly mechanism determination

To investigate the ecological processes driving bacterial assembly, we quantitatively inferred community assembly mechanisms by phylogenetic bin-based null model analysis of 16S rRNA gene amplicon data as described in refs. 95 , 96 . Longitudinal turnover in phylogenetic composition within the decomposition soil between successional stages was quantified using the beta nearest taxon index (βNTI), where a |βNTI| value <+2 indicates that stochastic forces drive community assembly and a value >+2 indicates less than or greater than expected phylogenetic turnover by random chance (deterministic forces). βNTI values <−2 correspond to homogeneous selection and values >+2 correspond to heterogeneous selection. Homogeneous selection refers to communities that are more similar to each other than expected by random chance, while heterogeneous selection refers to communities that are less similar to each other than expected by random chance. Deterministic forces include selection factors such as environmental filtering and biological interactions, while stochastic forces include random factors such as dispersal, birth–death events and immigration.

MAGs generation and classification

To maximize assembly, metagenomes were co-assembled within sites using MEGAHIT (v.1.2.9) 97 with the following flags: –k-min 41 (see Supplementary Tables 4 – 6 for a list of samples used to generate metagenomic data, co-assembly statistics, GTDB taxonomic classification and TPM-normalized count abundance of MAGs within each sample). Assembled scaffolds >2,500 kb were binned into MAGs using MetaBAT2 (v.2.12.1) 98 with default parameters. MAG completion and contamination were assessed using checkM (v.1.1.2) 99 . MAGs were conservatively kept in the local MAG database if they were >50% complete and <10% contaminated. MAGs were dereplicated at 99% identity using dRep (v.2.6.2) 100 . MAG taxonomy was assigned using GTDB-tk (v.2.0.0, r207) 101 . Novel taxonomies were determined as the first un-named taxonomic level in the GTDB classification string (see Supplementary Table 5 for MAG quality and taxonomy information). MAGs and co-assemblies were annotated using DRAM (v.1.0.0) 102 (Supplementary Table 5 ; https://doi.org/10.5281/zenodo.7843104 ). From 575 metagenomes, we recovered 1,130 MAGs, of which 276 were medium or high quality, and dereplicated these at 99% identity into 257 MAGs. This MAG set encompassed novel bacterial orders ( n  = 3), families ( n  = 9), genera ( n  = 28) and species ( n  = 158), providing genomic blueprints for microbial decomposers dominated by Gammaproteobacteria and Actinobacteriota (Supplementary Table 5 ).

MAG and gene abundance mapping

To determine the abundance of the MAGs in each sample, we mapped reads from each sample to the dereplicated MAG set using bowtie2 (v.2.3.5) 74 with the following flags: -D 10 -R 2 -N 1 -L 22 -i S,0,2.50. Output sam files were converted to sorted BAM files using samtools (v.1.9) 75 . BAM files were filtered for reads mapping at 95% identity using the reformat.sh script with flag idfilter=0.95 from BBMap (v.38.90) ( https://sourceforge.net/projects/bbmap/ ). Filtered BAM files were input to CoverM (v0.3.2) ( https://github.com/wwood/CoverM ) in genome mode to output transcripts per million (TPM). To determine the abundance of genes across samples, we clustered the gene nucleotide sequences from the annotated assemblies output by DRAM using MMseqs2 (release 13) easy-linclust (v4e23d5f1d13a435c7b6c9406137ed68ce297e0fc) 103 with the following flags: –min-seq-id 0.95–alignment-mode 3–max-seqs 100000. We then mapped reads to the cluster representative using bowtie2 (ref. 74 ) and filtered them to 95% identity as described above for the MAGs. To determine gene abundance, filtered bams were input to coverM in contig mode to output TPM. Bacterial MAG feature tables were imported into QIIME2 (v.2020.8) 79 . Bacterial features that were not present for a total of 50 times and were found in less than six samples were removed from the dataset to reduce noise. Bacterial feature tables were collapsed at the phylum, class, order, family, genus and species GTDB taxonomic levels. Community diversity was compared between the MAG and 16S rRNA ASV feature tables to ensure that both data types demonstrate the same biological signal. Each table was filtered to contain samples with paired 16S rRNA and metagenomic data (that is, samples with both metagenomic and 16S rRNA data). Bray–Curtis dissimilarity matrices were calculated for the TPM-normalized MAG abundance table and rarified 16S rRNA ASV table. Procrustes/PROTEST 104 , 105 and Mantel tests were performed between the PCoA ordinations and distance matrices, respectively 106 . Results showed that the datasets were not significantly different from each other and confirmed their shared biological signal (Extended Data Fig. 10 ).

Metabolic interaction simulations

Higher-order (20 microbial members) co-occurrence patterns were calculated from the MAG relative frequency tables of each decomposition stage (that is, early, active, advanced) for each facility using HiOrCo (v.1.0.0) (cut-off 0.001) ( https://github.com/cdanielmachado/HiOrCo ). HiOrCo provides 100 iterations of co-occurring MAG communities to improve simulation accuracy. No significantly co-occurring MAGs were detected at the FIRS facility during advanced decomposition; therefore, we continued the analyses using only early and active decomposition stages at FIRS. CarveMe (v.1.5.1) 107 was used to construct genome-scale metabolic models (GEMs) from each MAG using default parameters ( https://github.com/cdanielmachado/carveme ). GEMs from each co-occurring MAG community were input as a microbial community into SMETANA (v1.0.0) ( https://github.com/cdanielmachado/smetana ) to compute several metrics that describe the potential for metabolic cooperative and competitive interactions between community members as described in refs. 34 , 35 . Metrics include metabolic interaction potential (MIP), metabolic resource overlap (MRO), species coupling score (SCS), metabolite uptake score (MUS), metabolite production score (MPS) and SMETANA score. MIP calculates how many metabolites the species can share to decrease their dependency on external resources. MRO is a method of assessing metabolic competition by measuring the overlap between the minimal nutritional requirements of all member species on the basis of their genomes. SCS is a community size-dependent measurement of the dependency of one species in the presence of the others to survive. MUS measures how frequently a species needs to uptake a metabolite to survive. MPS is a binary measurement of the ability of a species to produce a metabolite. The individual SMETANA score is a combination of the SCS, MUS and MPS scores and gives a measure of certainty of a cross-feeding interaction (for example, species A receives metabolite X from species B). Simulations were created on the basis of a minimal medium, calculated using molecular weights, that supports the growth of both organisms, with the inorganic compounds hydrogen, water and phosphate excluded from analysis. A random null model analysis was performed to ensure that changes in co-occurring MAGs within each site and decomposition are driving interaction potential changes. For each site and decomposition stage, 100 20-member communities were generated by random selection without replacement using random.sample(). Simulations to calculate MIP and MRO were performed as above. A detailed investigation into the potential molecules being cross-fed was performed on the late stages of decomposition for each facility: temperate-climate advanced decomposition and semi-arid active decomposition stages.

Metabolic efficiency simulations

Metabolic models and the Constraint Based Reconstruction and Analysis (COBRA) toolbox (v.3.0) 108 were used to simulate differences in metabolic capabilities between samples that are spatiotemporally different. A general base growth medium, M 0 , containing a list of carbohydrates, amino acids, lipids and other vitamins and minerals adapted from a previous study 109 was used. From this base medium, carbohydrate-rich, M 1 , amino acid-rich, M 2 , and lipid-rich, M 3 , media were defined. The carbohydrate-rich medium includes all compounds in the base medium but allows for higher uptake of carbohydrates than proteins and lipids, and vice versa. The COBRA toolbox 108 in MATLAB was used to optimize overall ATP production from M 1 , M 2 and M 3 for each individual MAG in an aerobic condition. This assumption was made because the topsoil conditions in which decomposition happens are relatively aerobic. The calculated maximum ATP yields can be interpreted as the maximum capability of each MAG in extracting ATP from the growth media. Finally, the weighted average of total ATP production from the GEMs in a sample was calculated by multiplying the relative abundance of each MAG by the maximum total ATP production and summing over all of the GEMs in a sample 110 .

Molecular networking and spectral library search

A molecular network was created using the Feature-Based Molecular Networking (FBMN) workflow (v.28.2) 111 on GNPS ( https://gnps.ucsd.edu ; ref. 77 ). The mass spectrometry data were first processed with MZMINE2 (v.2.53) 112 and the results were exported to GNPS for FBMN analysis. The precursor ion mass tolerance was set to 0.05 Da and the MS/MS fragment ion tolerance to 0.05 Da. A molecular network was then created where edges were filtered to have a cosine score above 0.7 and >5 matched peaks. Furthermore, edges between two nodes were kept in the network if and only if each of the nodes appeared in each other’s respective top 10 most similar nodes. Finally, the maximum size of a molecular family was set to 100, and the lowest-scoring edges were removed from molecular families until the molecular family size was below this threshold. The spectra in the network were then searched against GNPS spectral libraries 77 , 111 . All matches kept between network spectra and library spectra were required to have a score above 0.7 and at least 6 matched peaks.

Metabolite formula and class prediction

Spectra were downloaded from GNPS and imported to SIRIUS (v.4.4) 113 containing ZODIAC 114 for database-independent molecular formula annotation under default parameters. Formula annotations were kept if the ZODIAC score was at least 0.95 and at least 90% of the MS/MS spectrum intensity was explained by SIRIUS as described by the less-restrictive filtering from ref. 114 . A final list of formula identifications was created by merging ZODIAC identifications with library hits from GNPS (Supplementary Table 36 ). In the cases where a metabolite had both a ZODIAC predicted formula and an assigned library hit, the library hit assignment took precedence. The final formula list contained 604 formula assignments. Organic compound composition was examined in van Krevelen diagrams and assigned to major biochemical classes on the basis of the molar H:C and O:C ratios 115 . Since classification based on molecular ratio does not guarantee that the compound is part of a specific biochemical class, compounds were labelled as chemically similar by adding ‘-like’ to their assigned class (for example, protein-like). Furthermore, compound formulas were used to calculate the nominal oxidation state of carbon on the basis of the molecular abundances of C, H, N, O, P and S as described in ref. 116 (Supplementary Tables 37 and 38 ).

Metabolite feature table processing

The metabolite feature table downloaded from GNPS was normalized using sum normalization, then scaled with pareto scaling 117 and imported in QIIME2 (v.2022.2) 79 . This table contains all library hits, metabolites with predicted formulas and unannotated metabolites. PCoA clustering with Bray–Curtis and Jaccard distances confirmed clustering of processing controls separate from soil and skin samples. Five soil samples were removed for clustering with processing controls. Processing controls were removed from the dataset; then metabolites absent from a minimum of 30 samples were removed to reduce noise. Bray–Curtis and Jaccard beta diversity group comparisons were performed between soil and skin samples using PERMANOVA (perm. = 999). The metabolite feature table was filtered to contain metabolites with chemical formulas based on GNPS library hits and/or predicted chemical formulas from ZODIAC. Differential abundance analyses were performed on these tables from the cadaver-associated soil and skin to test metabolite log-ratio change over decomposition stage using initial, day 0 samples as the reference frame, utilizing the Analysis of Composition of Microbiomes with Bias Correction (ANCOM-BC) 118 QIIME2 (v.2022.2) plugin.

The complete methodology including mathematical formulas for joint-RPCA can be found in Supplementary Text . Briefly, before joint factorization, we first split the dataset into training train and testing sample sets from the total set of shared samples across all input data matrices. The datasets included in this analysis were 16S rRNA gene abundances, 18S rRNA gene abundances, MAG abundances, MAG gene abundances, MAG gene functional modules and metabolites from the hip-adjacent decomposition soil. Each matrix was then transformed through the robust-centred-log-ratio transformation (robust-clr) to centre the data around zero and approximate a normal distribution 42 , 119 . Unlike the traditional clr transformation, the robust-clr handles the sparsity often found in biological data without requiring imputation. The robust-clr transformation was applied to the training and test set matrices independently. The joint factorization used here was built on the OptSpace matrix completion algorithm, which is a singular value decomposition optimized on a local manifold 42 , 119 . A shared matrix was estimated across the shared samples of all input matrices. For each matrix, the observed values were only computed on the non-zero entries and then averaged, such that the minimized shared estimated matrices were optimized across all matrices. The minimization was performed across iterations by gradient descent. To ensure that the rotation of the estimated matrices was consistent, the estimated shared matrix and the matrix of shared eigenvalues across all input matrices were recalculated at each iteration. To prevent overfitting of the joint-factorization, cross-validation of the reconstruction was performed. In this case, all the previously described minimization was performed on only the training set data. The test set data were then projected into the same space using the training set data estimated matrices and the reconstruction of the test data was calculated. Through this, it can be ensured that the minimization error of the training data estimations also minimizes that of the test set data, which is not incorporated into these estimates on each iteration. After the training data estimates were finalized, the test set samples were again projected into the final output to prevent these samples from being lost. The correlations of all features across all input matrices were calculated from the final estimated matrices. Finally, here we treated the joint-RPCA with only one input matrix as the original RPCA 119 but with the additional benefit of the addition of cross-validation for comparison across other methods.

Multi-omics ecological network visualization

The datasets included in this analysis were 18S rRNA gene abundances, MAG abundances, MAG gene functional modules and metabolites from the hip-adjacent decomposition soil. log ratios were generated using the joint-RPCA PC2 scores, chosen on the basis of the sample ordination, to rank each omics feature on the basis of association with either initial non-decomposition and early decomposition soil or late decomposition (that is, active and advanced) soil time periods. The log ratios are the log ratio of the sum of the top N -features raw-counts/table-values over the sum of the bottom N ranked features raw-counts/table-values, based on the PC2 loadings produced from the ordinal analysis since these were observed to change the most by decomposition stage. To prevent sample drop out in the log ratio due to sparsity, as described in refs. 120 , 121 , between 2 and 1,500 numerator and denominator features for each omic were summed such that at least 90% of the sample were retained: metagenomics (MAGs) N -features = 30 (99.2%), 18S N -features = 1,499 (90.1%), metagenomics (gene modules) N -features = 26 (100%) and metabolomics N -features = 238 (100%). The joint-RPCA correlation matrix was subset down to the total initial day zero, early, active or advanced decomposition-associated features used in the log ratios to generate the network visualizations. Only the top 20% of correlations between selected nodes were retained to reduce noise in generating the network visualization.

Phylogenetic tree generation

Redbiom (v.0.3.9) 122 was used to search for all publicly available AGP 90 and EMP 69 studies for samples containing at least 100 counts of a key decomposer. The AGP samples were further filtered to only include gut and skin environments and the EMP samples were limited to only include soil and host environment. Next, the top 50 most abundant ASVs were taken from each environment along with the key decomposers and placed on a phylogenetic tree using Greengenes2 (release 2022.10) 123 . The ASVs were then ranked according to the number of samples they were found in and visualized using EMPress (v.1.2.0) 124 .

Random forest regression modelling

Processed features tables from each ‘omic data type were used for random forest regression modelling with nested cross-validation (CV) to test ADD prediction power. Data were subset so that models were trained and tested for each sampling location separately (for example, soil adjacent to the hip, soil adjacent to the face, skin of the hip and skin of the face). Data were pre-processed for models using calour (v.2018.5.1) ( http://biocore.github.io/calour/index.html ) and models were trained/tested using scikit-learn (v.0.24.2) 125 . Features with an abundance of zero in the dataset after filtering were removed. The facilities at which sampling was performed were included as features in the model to determine whether geographical location is important for modelling. Samples from individual bodies were grouped together to prevent samples from a body being split between train and test sets to help prevent overfitting. Nested CV was performed to thoroughly test the accuracy and generalizability of the models. Hyperparameters tested for optimization were: max_depth = [None, 4], max_features = [‘auto’, 0.2] and bootstrap = [True, False]. Nested CV was made of an outer CV loop and an inner CV loop. The outer loop was created by a LeaveOneGroupOut split wherein samples from one of the 36 bodies were set aside for model validation after the inner CV loop completes. The remaining 35 bodies were used for RandomForestRegressor (n_estimators = 500) model training with the inner CV loop. The inner CV loop performed a LeaveOneGroupOut split as well so that 34 bodies were used to train a model, which was tested on the samples from the one withheld body in the inner CV loop. This inner CV was repeated until all 35 bodies within the inner loop were used as a test body once to determine which hyperparameters were best for prediction. The best-performing inner CV model was then used to predict the samples from the 36th body that was withheld at the outer CV loop, which now acts as a validation test set. Model accuracy was determined by calculating the MAE of the predicted ADD relative to the actual ADD of all the validation body samples. The prediction of the samples from the 36th body, which was completely withheld from the training of the model, allowed us to reduce overfitting and gain an estimate of the model accuracy. The entire nested CV process was repeated until each body was used as the outer CV loop validation body one time (that is, 36 iterations). The resulting 36 mean absolute errors of each body were used for determining model accuracy, generalizability and which data type performed the best. To ensure that we were using the complete dataset to determine the important taxa driving the models, the best-performing hyperparameters (bootstrap=False, max_depth=None, max_features=0.2) were used to train a RandomForestRegressor (n_estimators = 1,000) model to extract the important features. Important features were ranked by their relative importance on a scale from 0–1, where the sum of all importances equals 1. A random forest model using TBS from each sampling day as training data for ADD prediction was trained and tested using the same methodology to compare microbiome-based models to a more traditional method of assessing decomposition progression.

Lastly, we confirmed the accuracy and reliability of postmortem interval prediction with an independent test set of samples collected from bodies not represented in our models. The independent test set was collected from hip-adjacent soil and skin of the hip locations across three facilities (ARF, Forensic Anthropology Research Facility in San Marcos, Texas (FARF) and Research on Experimental and Social Thanatology in Quebec, Canada (REST)) (Supplementary Table 39 ). The independent test set was made up of temporal samples taken from each facility. ARF and REST samples consisted of three bodies with three timepoints taken from each body at each facility. At each timepoint, a soil sample was swabbed within the purge and outside the purge, and a skin sample was swabbed from the hip. One ARF body (B3.D4) did not have purge during the first timepoint; therefore, this sample was not collected. FARF provided samples from four bodies. Two bodies (2021.04 and 2021.45) had the same sampling procedure as ARF and REST, while the other two bodies (2021.39 and 2021.44) did not have purge during the first sampling timepoint; hence samples were not collected. Samples were collected, shipped, stored, DNA extracted and 16S rRNA V4 sequenced using the previously described methods. After data generation, amplicon sequence data were analysed in the Metcalf lab using QIIME2 (v.2020.8) 79 . Sequences were quality filtered and demultiplexed using the pre-assigned Golay barcodes. Reads were 150 bp in length. Sequences were then classified into ASVs using the deblur denoising method 80 . Taxonomic identifiers were assigned to the ASVs using the QIIME feature-classifier classify-sklearn method 81 using the SILVA 132 99% classifier for the 515fb/806rb gene sequences. ASVs that were assigned to chloroplast or mitochondria (non-microbial sequences) were filtered out of the dataset before continuing analysis. Data were rarified to 5,000 reads per sample and collapsed to the SILVA database 7-rank taxonomic level (L7). Feature tables were split into soil and skin data; then the validation data table was matched to the original dataset so that sampling location and features were the same (that is, using only taxa found in hip-adjacent soil in both datasets). A random forest regressor model (n_estimators=1000, max_depth=None, bootstrap=False, max_features=0.2) was built and fitted to predict the validation samples’ true ADD measurement. Randomly assigned ADDs were used as a null model.

Statistics and reproducibility

From March 2016 to December 2017, 36 human cadavers were sampled daily starting on the day of placement through 21 d of decomposition. The study encompasses three geographically distinct anthropological research facilities, and 3 cadavers were placed at each facility for each of the four seasons. Swab samples were collected from soil directly adjacent to the hip, face and a control, non-decomposition location. Swab samples were also collected from skin located on the hip and the face. No statistical method was used to predetermine sample size. The samples were randomized during processing. The investigators were not blinded to allocation during experiments and outcome assessment. Samples were excluded if not enough DNA was extracted, sequenced or if sequence quality was poor. Negative controls were included during DNA/metabolite extraction, amplification and library preparation. Linear statistical modelling was performed with linear mixed-effects models to a single dependent variable, and response variables were statistically assessed over ADD with a random intercept for individual bodies to account for repeated measures. Group comparisons were performed using Dunn Kruskal–Wallis H -test with multiple-comparison P values adjusted using the Benjamini–Hochberg method, two-tailed analysis of variance (ANOVA) with no multiple-comparison adjustments, or PERMANOVA with a multiple-testing correction. Differential abundance analyses were performed using ANCOM-BC 118 with initial, day 0 samples as the reference frame. Procrustes/PROTEST 104 , 105 and Mantel tests were performed between PCoA ordinations and distance matrices, respectively 106 .

Reporting summary

Further information on research design is available in the Nature Portfolio Reporting Summary linked to this article.

Data availability

Raw amplicon and metagenomic sequencing data and sample metadata are available on the QIITA open-source microbiome study management platform under study 14989 and ENA accession PRJEB62460 ( ERP147550 ). Dereplicated MAGs and DRAM output can be found publicly on Zenodo ( https://doi.org/10.5281/zenodo.7843104 ; https://zenodo.org/record/7938240 ) and NCBI BioProject PRJNA973116 . The mass spectrometry data were deposited on the MassIVE public repository (accession numbers: MSV000084322 for skin samples and MSV000084463 for soil samples). The molecular networking job can be publicly accessed at https://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=1c73926f2eb5409985cc2e136062db2f . The GNPS database was accessed through https://gnps.ucsd.edu/ . The GreenGenes2 database can be found at https://ftp.microbio.me/greengenes_release/ . SILVA databases can be found at https://www.arb-silva.de/documentation/release-1381/ . The Earth Microbiome Project data and American Gut Project data can be found on EBI under accessions ERP125879 and ERP012803 , respectively. 16S rRNA gene amplicon sequence data files from refs. 6 , 24 , 25 , 64 , 69 , 90 , 91 were obtained from QIITA 92 under study IDs 10141–10143 (ref. 6 ), 1609 (refs. 24 , 25 ), 13114 (ref. 69 ), 10317 (ref. 90 ), 13301 (ref. 64 ) and 11204 (ref. 91 ). Data from ref. 16 were obtained from the NCBI Sequence Read Archive under BioProject PRJNA525153 . Data from ref. 26 were obtained from the Max Planck Society Edmond repository ( https://edmond.mpdl.mpg.de/dataset.xhtml?persistentId=doi:10.17617/3.UV4FBN ). The GTDB data can be accessed at https://data.gtdb.ecogenomic.org/releases/ . Source data are provided with this paper.

Code availability

Analysis code, intermediate files and metadata are publicly available on Github ( https://github.com/Metcalf-Lab/2023-Universal-microbial-decomposer-network ). The complete mathematical algorithms for Joint-RPCA can be found in Supplementary Text .

Swift, M. J., Heal, O. W. & Anderson, J. M. Decomposition in Terrestrial Ecosystems (Blackwell Scientific, 1979).

Carter, D. O., Yellowlees, D. & Tibbett, M. Cadaver decomposition in terrestrial ecosystems. Naturwissenschaften 94 , 12–24 (2007).

Article   CAS   PubMed   Google Scholar  

Wagg, C., Schlaeppi, K., Banerjee, S., Kuramae, E. E. & van der Heijden, M. G. A. Fungal–bacterial diversity and microbiome complexity predict ecosystem functioning. Nat. Commun. 10 , 4841 (2019).

Article   PubMed   PubMed Central   Google Scholar  

Schroeter, S. A. et al. Microbial community functioning during plant litter decomposition. Sci. Rep. 12 , 7451 (2022).

Article   CAS   PubMed   PubMed Central   Google Scholar  

Strickland, M. S., Lauber, C., Fierer, N. & Bradford, M. A. Testing the functional significance of microbial community composition. Ecology 90 , 441–451 (2009).

Article   PubMed   Google Scholar  

Metcalf, J. L. et al. Microbial community assembly and metabolic function during mammalian corpse decomposition. Science 351 , 158–162 (2016).

Pechal, J. L. et al. The potential use of bacterial community succession in forensics as described by high throughput metagenomic sequencing. Int. J. Leg. Med. 128 , 193–205 (2014).

Article   Google Scholar  

Bar-On, Y. M., Phillips, R. & Milo, R. The biomass distribution on Earth. Proc. Natl Acad. Sci. USA 115 , 6506–6511 (2018).

Parmenter, R. R. & MacMahon, J. A. Carrion decomposition and nutrient cycling in a semiarid shrub–steppe ecosystem. Ecol. Monogr. 79 , 637–661 (2009).

Barton, P. S., Cunningham, S. A., Lindenmayer, D. B. & Manning, A. D. The role of carrion in maintaining biodiversity and ecological processes in terrestrial ecosystems. Oecologia 171 , 761–772 (2013).

Barton, P. S. et al. Towards quantifying carrion biomass in ecosystems. Trends Ecol. Evol. 34 , 950–961 (2019).

Putman, R. J. Flow of energy and organic matter from a carcase during decomposition: decomposition of small mammal carrion in temperate systems 2. Oikos 31 , 58–68 (1978).

Article   CAS   Google Scholar  

DeVault, T. L., Brisbin, I. L. Jr & Rhodes, O. E. Jr Factors influencing the acquisition of rodent carrion by vertebrate scavengers and decomposers. Can. J. Zool. 82 , 502–509 (2004).

Aneja, M. K. et al. Microbial colonization of beech and spruce litter—influence of decomposition site and plant litter species on the diversity of microbial community. Microb. Ecol. 52 , 127–135 (2006).

Banerjee, S. et al. Network analysis reveals functional redundancy and keystone taxa amongst bacterial and fungal communities during organic matter decomposition in an arable soil. Soil Biol. Biochem. 97 , 188–198 (2016).

Dangerfield, C. R., Frehner, E. H., Buechley, E. R., Şekercioğlu, Ç. H. & Brazelton, W. J. Succession of bacterial communities on carrion is independent of vertebrate scavengers. PeerJ 8 , e9307 (2020).

Johnson, H. R. et al. A machine learning approach for using the postmortem skin microbiome to estimate the postmortem interval. PLoS ONE 11 , e0167370 (2016).

Metcalf, J. L. et al. A microbial clock provides an accurate estimate of the postmortem interval in a mouse model system. eLife 2 , e01104 (2013).

Singh, B. et al. Temporal and spatial impact of human cadaver decomposition on soil bacterial and arthropod community structure and function. Front. Microbiol. 8 , 2616 (2017).

Hong, E. S., Bang, S. H., Kim, Y.-H. & Min, J. Treatment of livestock carcasses in soil using Corynebacterium glutamicum and lysosomal application to livestock burial. Environ. Health Toxicol. 33 , e2018009 (2018).

Fey, S. B. et al. Recent shifts in the occurrence, cause, and magnitude of animal mass mortality events. Proc. Natl Acad. Sci. USA 112 , 1083–1088 (2015).

Metcalf, J. L. Estimating the postmortem interval using microbes: knowledge gaps and a path to technology adoption. Forensic Sci. Int. Genet. 38 , 211–218 (2019).

Beck, H. E. et al. Present and future Köppen-Geiger climate classification maps at 1-km resolution. Sci. Data 5 , 180214 (2018).

Weiss, S., Carter, D. O., Metcalf, J. L. & Knight, R. Carcass mass has little influence on the structure of gravesoil microbial communities. Int. J. Leg. Med. 130 , 253–263 (2015).

Carter, D. O., Metcalf, J. L., Bibat, A. & Knight, R. Seasonal variation of postmortem microbial communities. Forensic Sci. Med. Pathol. 11 , 202–207 (2015).

Shukla, S. P. et al. Microbiome-assisted carrion preservation aids larval development in a burying beetle. Proc. Natl Acad. Sci. USA 115 , 11274–11279 (2018).

Megyesi, M. S., Nawrocki, S. P. & Haskell, N. H. Using accumulated degree-days to estimate the postmortem interval from decomposed human remains. J. Forensic Sci. 50 , 618–626 (2005).

Connor, M., Baigent, C. & Hansen, E. S. Measuring desiccation using qualitative changes: a step toward determining regional decomposition sequences. J. Forensic Sci. 64 , 1004–1011 (2019).

Towne, E. G. Prairie vegetation and soil nutrient responses to ungulate carcasses. Oecologia 122 , 232–239 (2000).

Vass, A. A., Bass, W. M., Wolt, J. D., Foss, J. E. & Ammons, J. T. Time since death determinations of human cadavers using soil solution. J. Forensic Sci. 37 , 1236–1253 (1992).

Coe, M. The decomposition of elephant carcases in the Tsavo (East) National Park, Kenya. J. Arid Environ. 1 , 71–86 (1978).

Cotrufo, M. F., Wallenstein, M. D., Boot, C. M., Denef, K. & Paul, E. The Microbial Efficiency-Matrix Stabilization (MEMS) framework integrates plant litter decomposition with soil organic matter stabilization: do labile plant inputs form stable soil organic matter? Glob. Change Biol. 19 , 988–995 (2013).

Gralka, M., Szabo, R., Stocker, R. & Cordero, O. X. Trophic interactions and the drivers of microbial community assembly. Curr. Biol. 30 , R1176–R1188 (2020).

Zelezniak, A. et al. Metabolic dependencies drive species co-occurrence in diverse microbial communities. Proc. Natl Acad. Sci. USA 112 , 6449–6454 (2015).

Machado, D. et al. Polarization of microbial communities between competitive and cooperative metabolism. Nat. Ecol. Evol. 5 , 195–203 (2021).

DeBruyn, J. M. et al. Comparative decomposition of humans and pigs: soil biogeochemistry, microbial activity and metabolomic profiles. Front. Microbiol. 11 , 608856 (2020).

Keenan, S. W., Schaeffer, S. M., Jin, V. L. & DeBruyn, J. M. Mortality hotspots: nitrogen cycling in forest soils during vertebrate decomposition. Soil Biol. Biochem. 121 , 165–176 (2018).

Carbonero, F., Benefiel, A. C., Alizadeh-Ghamsari, A. H. & Gaskins, H. R. Microbial pathways in colonic sulfur metabolism and links with health and disease. Front. Physiol. 3 , 448 (2012).

Parr, W. R. G. J. Water Potential Relations in Soil Microbiology (Soil Science Society of America, 1981).

Stark, J. M. & Firestone, M. K. Mechanisms for soil moisture effects on activity of nitrifying bacteria. Appl. Environ. Microbiol. 61 , 218–221 (1995).

Manzoni, S., Taylor, P., Richter, A., Porporato, A. & Ågren, G. I. Environmental and stoichiometric controls on microbial carbon-use efficiency in soils. New Phytol. 196 , 79–91 (2012).

Martino, C. et al. A novel sparse compositional technique reveals microbial perturbations. mSystems 4 , e00016–e00019 (2019).

Drobish, A. M. et al. Oblitimonas alkaliphila gen. nov., sp. nov., in the family Pseudomonadaceae, recovered from a historical collection of previously unidentified clinical strains. Int. J. Syst. Evol. Microbiol. 66 , 3063–3070 (2016).

Ashe, E. C., Comeau, A. M., Zejdlik, K. & O’Connell, S. P. Characterization of bacterial community dynamics of the human mouth throughout decomposition via metagenomic, metatranscriptomic, and culturing techniques. Front. Microbiol. 12 , 689493 (2021).

Dong, N. et al. Prevalence, transmission, and molecular epidemiology of tet(X)-positive bacteria among humans, animals, and environmental niches in China: an epidemiological, and genomic-based study. Sci. Total Environ. 818 , 151767 (2022).

Cobaugh, K. L., Schaeffer, S. M. & DeBruyn, J. M. Functional and structural succession of soil microbial communities below decomposing human cadavers. PLoS ONE 10 , e0130201 (2015).

Keenan, S. W. et al. Spatial impacts of a multi-individual grave on microbial and microfaunal communities and soil biogeochemistry. PLoS ONE 13 , e0208845 (2018).

Tomberlin, J. K. et al. Interkingdom responses of flies to bacteria mediated by fly physiology and bacterial quorum sensing. Anim. Behav. 84 , 1449–1456 (2012).

Shi, Z. et al. Putrescine is an intraspecies and interkingdom cell–cell communication signal modulating the virulence of Dickeya zeae . Front. Microbiol. 10 , 1950 (2019).

Valdés-Santiago, L. & Ruiz-Herrera, J. Stress and polyamine metabolism in fungi. Front. Chem. 1 , 42 (2013).

PubMed   Google Scholar  

Tofalo, R., Cocchi, S. & Suzzi, G. Polyamines and gut microbiota. Front. Nutr. 6 , 16 (2019).

Challacombe, J. F. et al. Genomes and secretomes of Ascomycota fungi reveal diverse functions in plant biomass decomposition and pathogenesis. BMC Genomics 20 , 976 (2019).

Fu, X. et al. Fungal succession during mammalian cadaver decomposition and potential forensic implications. Sci. Rep. 9 , 12907 (2019).

Fierer, N. et al. Cross-biome metagenomic analyses of soil microbial communities and their functional attributes. Proc. Natl Acad. Sci. USA 109 , 21390–21395 (2012).

Dini-Andreote, F., Stegen, J. C., van Elsas, J. D. & Salles, J. F. Disentangling mechanisms that mediate the balance between stochastic and deterministic processes in microbial succession. Proc. Natl Acad. Sci. USA 112 , E1326–E1332 (2015).

Zhou, J. & Ning, D. Stochastic community assembly: does it matter in microbial ecology? Microbiol. Mol. Biol. Rev . https://doi.org/10.1128/mmbr.00002-17 (2017).

Zhou, J. et al. Stochasticity, succession, and environmental perturbations in a fluidic ecosystem. Proc. Natl Acad. Sci. USA 111 , E836–E845 (2014).

Waring, B., Gee, A., Liang, G. & Adkins, S. A quantitative analysis of microbial community structure–function relationships in plant litter decay. iScience 25 , 104523 (2022).

Aerts, R. Climate, leaf litter chemistry and leaf litter decomposition in terrestrial ecosystems: a triangular relationship. Oikos 79 , 439–449 (1997).

Purahong, W. et al. Life in leaf litter: novel insights into community dynamics of bacteria and fungi during litter decomposition. Mol. Ecol. 25 , 4059–4074 (2016).

Pechal, J. L., Crippen, T. L., Cammack, J. A., Tomberlin, J. K. & Benbow, M. E. Microbial communities of salmon resource subsidies and associated necrophagous consumers during decomposition: potential of cross-ecosystem microbial dispersal. Food Webs 19 , e00114 (2019).

Hyde, E. R., Haarmann, D. P., Petrosino, J. F., Lynne, A. M. & Bucheli, S. R. Initial insights into bacterial succession during human decomposition. Int. J. Leg. Med. 129 , 661–671 (2015).

Vogel, H. et al. The digestive and defensive basis of carcass utilization by the burying beetle and its microbiota. Nat. Commun. 8 , 15186 (2017).

Deel, H. L. et al. The microbiome of fly organs and fly–human microbial transfer during decomposition. Forensic Sci. Int. 340 , 111425 (2022).

Mason, A. R. et al. Body mass index (BMI) impacts soil chemical and microbial response to human decomposition. mSphere 7 , e0032522 (2022).

Burkepile, D. E. et al. Chemically mediated competition between microbes and animals: microbes as consumers in food webs. Ecology 87 , 2821–2831 (2006).

Caporaso, J. G. et al. Ultra-high-throughput microbial community analysis on the Illumina HiSeq and MiSeq platforms. ISME J. 6 , 1621–1624 (2012).

Walters, W. et al. Improved bacterial 16S rRNA gene (V4 and V4-5) and fungal internal transcribed spacer marker gene primers for microbial community surveys. mSystems https://doi.org/10.1128/msystems.00009-15 (2016).

Thompson, L. R. et al. A communal catalogue reveals Earth’s multiscale microbial diversity. Nature 551 , 457–463 (2017).

Amaral-Zettler, L. A., McCliment, E. A., Ducklow, H. W. & Huse, S. M. A method for studying protistan diversity using massively parallel sequencing of V9 hypervariable regions of small-subunit ribosomal RNA genes. PLoS ONE 4 , e6372 (2009).

Sanders, J. G. et al. Optimizing sequencing protocols for leaderboard metagenomics by combining long and short reads. Genome Biol. 20 , 226 (2019).

Glenn, T. C. et al. Adapterama I: universal stubs and primers for 384 unique dual-indexed or 147,456 combinatorially-indexed Illumina libraries (iTru & iNext). PeerJ 7 , e7755 (2019).

Didion, J. P., Martin, M. & Collins, F. S. Atropos: specific, sensitive, and speedy trimming of sequencing reads. PeerJ 5 , e3720 (2017).

Langmead, B. & Salzberg, S. L. Fast gapped-read alignment with Bowtie 2. Nat. Methods 9 , 357–359 (2012).

Li, H. et al. The Sequence Alignment/Map format and SAMtools. Bioinformatics 25 , 2078–2079 (2009).

Quinlan, A. R. & Hall, I. M. BEDTools: a flexible suite of utilities for comparing genomic features. Bioinformatics 26 , 841–842 (2010).

Wang, M. et al. Sharing and community curation of mass spectrometry data with Global Natural Products Social Molecular Networking. Nat. Biotechnol. 34 , 828–837 (2016).

Sumner, L. W. et al. Proposed minimum reporting standards for chemical analysis Chemical Analysis Working Group (CAWG) Metabolomics Standards Initiative (MSI). Metabolomics 3 , 211–221 (2007).

Bolyen, E. et al. Reproducible, interactive, scalable and extensible microbiome data science using QIIME 2. Nat. Biotechnol. 37 , 852–857 (2019).

Amir, A. et al. Deblur rapidly resolves single-nucleotide community sequence patterns. mSystems 2 , e00191-16 (2017).

Bokulich, N. A. et al. Optimizing taxonomic classification of marker-gene amplicon sequences with QIIME 2’s q2-feature-classifier plugin. Microbiome 6 , 90 (2018).

Robeson, M. S. 2nd et al. RESCRIPt: reproducible sequence taxonomy reference database management. PLoS Comput. Biol. 17 , e1009581 (2021).

Janssen, S. et al. Phylogenetic placement of exact amplicon sequences improves associations with clinical information. mSystems 3 , e00021-18 (2018).

Kruskal, W. H. & Wallis, W. A. Use of ranks in one-criterion variance analysis. J. Am. Stat. Assoc. 47 , 583–621 (1952).

Chen, J. et al. Associating microbiome composition with environmental covariates using generalized UniFrac distances. Bioinformatics 28 , 2106–2113 (2012).

Anderson, M. J. A new method for non‐parametric multivariate analysis of variance. Austral Ecol. 26 , 32–46 (2001).

Google Scholar  

Wickham, H. Ggplot2. Wiley Interdiscip. Rev. Comput. Stat. 3 , 180–185 (2011).

R Core Team. R: A Language and Environment for Statistical Computing (R Foundation for Statistical Computing, 2020).

Vázquez-Baeza, Y., Pirrung, M., Gonzalez, A. & Knight, R. EMPeror: a tool for visualizing high-throughput microbial community data. Gigascience 2 , 16 (2013).

McDonald, D. et al. American Gut: an open platform for citizen science microbiome research. mSystems 3 , e00031-18 (2018).

Kodama, W. A. et al. Trace evidence potential in postmortem skin microbiomes: from death scene to morgue. J. Forensic Sci. 64 , 791–798 (2019).

Gonzalez, A. et al. Qiita: rapid, web-enabled microbiome meta-analysis. Nat. Methods 15 , 796–798 (2018).

Martin, M. Cutadapt removes adapter sequences from high-throughput sequencing reads. EMBnet. J. 17 , 10–12 (2011).

Kluyver, T. et al. in Positioning and Power in Academic Publishing: Players, Agents and Agendas (eds Loizides, F. & Scmidt, B.) 87–90 (IOS Press, 2016).

Stegen, J. C. et al. Quantifying community assembly processes and identifying features that impose them. ISME J. 7 , 2069–2079 (2013).

Stegen, J. C., Lin, X., Fredrickson, J. K. & Konopka, A. E. Estimating and mapping ecological processes influencing microbial community assembly. Front. Microbiol. 6 , 370 (2015).

Li, D., Liu, C.-M., Luo, R., Sadakane, K. & Lam, T.-W. MEGAHIT: an ultra-fast single-node solution for large and complex metagenomics assembly via succinct de Bruijn graph. Bioinformatics 31 , 1674–1676 (2015).

Kang, D. D. et al. MetaBAT 2: an adaptive binning algorithm for robust and efficient genome reconstruction from metagenome assemblies. PeerJ 7 , e7359 (2019).

Parks, D. H., Imelfort, M., Skennerton, C. T., Hugenholtz, P. & Tyson, G. W. CheckM: assessing the quality of microbial genomes recovered from isolates, single cells, and metagenomes. Genome Res. 25 , 1043–1055 (2015).

Olm, M. R., Brown, C. T., Brooks, B. & Banfield, J. F. dRep: a tool for fast and accurate genomic comparisons that enables improved genome recovery from metagenomes through de-replication. ISME J. 11 , 2864–2868 (2017).

Chaumeil, P.-A., Mussig, A. J., Hugenholtz, P. & Parks, D. H. GTDB-Tk: a toolkit to classify genomes with the Genome Taxonomy Database. Bioinformatics 36 , 1925–1927 (2019).

Shaffer, M. et al. DRAM for distilling microbial metabolism to automate the curation of microbiome function. Nucleic Acids Res. 48 , 8883–8900 (2020).

Steinegger, M. & Söding, J. MMseqs2 enables sensitive protein sequence searching for the analysis of massive data sets. Nat. Biotechnol. 35 , 1026–1028 (2017).

Gower, J. C. Generalized procrustes analysis. Psychometrika 40 , 33–51 (1975).

Jackson, D. A. PROTEST: a PROcrustean Randomization TEST of community environment concordance. Écoscience 2 , 297–303 (1995).

Peres-Neto, P. R. & Jackson, D. A. How well do multivariate data sets match? The advantages of a Procrustean superimposition approach over the Mantel test. Oecologia 129 , 169–178 (2001).

Machado, D., Andrejev, S., Tramontano, M. & Patil, K. R. Fast automated reconstruction of genome-scale metabolic models for microbial species and communities. Nucleic Acids Res. 46 , 7542–7553 (2018).

Heirendt, L. et al. Creation and analysis of biochemical constraint-based models using the COBRA Toolbox v.3.0. Nat. Protoc. 14 , 639–702 (2019).

Bittinger, K. et al. Bacterial colonization reprograms the neonatal gut metabolome. Nat. Microbiol. 5 , 838–847 (2020).

Chan, S. H. J., Simons, M. N. & Maranas, C. D. SteadyCom: predicting microbial abundances while ensuring community stability. PLoS Comput. Biol. 13 , e1005539 (2017).

Nothias, L.-F. et al. Feature-based molecular networking in the GNPS analysis environment. Nat. Methods 17 , 905–908 (2020).

Pluskal, T., Castillo, S., Villar-Briones, A. & Oresic, M. MZmine 2: modular framework for processing, visualizing, and analyzing mass spectrometry-based molecular profile data. BMC Bioinformatics 11 , 395 (2010).

Dührkop, K. et al. SIRIUS 4: a rapid tool for turning tandem mass spectra into metabolite structure information. Nat. Methods 16 , 299–302 (2019).

Ludwig, M. et al. Database-independent molecular formula annotation using Gibbs sampling through ZODIAC. Nat. Mach. Intell. 2 , 629–641 (2020).

Kim, S., Kramer, R. W. & Hatcher, P. G. Graphical method for analysis of ultrahigh-resolution broadband mass spectra of natural organic matter, the van Krevelen diagram. Anal. Chem. 75 , 5336–5344 (2003).

Boye, K. et al. Thermodynamically controlled preservation of organic carbon in floodplains. Nat. Geosci. 10 , 415–419 (2017).

van den Berg, R. A., Hoefsloot, H. C. J., Westerhuis, J. A., Smilde, A. K. & van der Werf, M. J. Centering, scaling, and transformations: improving the biological information content of metabolomics data. BMC Genomics 7 , 142 (2006).

Lin, H. & Peddada, S. D. Analysis of compositions of microbiomes with bias correction. Nat. Commun. 11 , 3514 (2020).

Keshavan, R. H., Montanari, A. & Oh, S. Matrix completion from a few entries. IEEE Trans. Inf. Theory 56 , 2980–2998 (2010).

Fedarko, M. W. et al. Visualizing ’omic feature rankings and log-ratios using Qurro. NAR Genom. Bioinform. 2 , lqaa023 (2020).

Martino, C. et al. Context-aware dimensionality reduction deconvolutes gut microbial community dynamics. Nat. Biotechnol. 39 , 165–168 (2021).

McDonald, D. et al. redbiom: a rapid sample discovery and feature characterization system. mSystems 4 , e00215–e00219 (2019).

McDonald, D. et al. Greengenes2 unifies microbial data in a single reference tree. Nat. Biotechnol. https://doi.org/10.1038/s41587-023-01845-1 (2023).

Cantrell, K. et al. EMPress enables tree-guided, interactive, and exploratory analyses of multi-omic data sets. mSystems 6 , e01216–e01220 (2021).

Pedregosa, F., Varoquaux, G. & Gramfort, A. Scikit-learn: machine learning in Python. J. Mach. Learn. Res. 12 , 2825–2830 (2011).

Download references

Acknowledgements

Foremost, we thank the willed-body donors for their contribution to science; A. Esterle, K. Otto, H. Archer, C. Carter, R. Reibold, L. Burcham, J. Prenni and the CSU Writes programme for technical and resource contributions; A. Buro, V. Rodriguez, M. Sarles, A. Hartman and A. Uva at SHSU for field contributions. Opinions or points of view expressed here represent a consensus of the authors and do not necessarily represent the official position or policies of the US Department of Justice. Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the US Government. Funding was provided by the National Institutes of Justice (2016-DN-BX-0194, J.L.M.; 2015-DN-BX-K016, J.L.M.; GRF STEM 2018-R2-CX-0017, A.D.B.; GRF STEM 2018-R2-CX-0018, H.L.D.), the Canadian Institute for Advanced Research Global Scholar Program (J.L.M.), National Science Foundation Early Career Award (1912915, K. C. Wrighton) and National Institutes of Health T32 Training Award (T32GM132057, V.N.).

Author information

Authors and affiliations.

Department of Animal Sciences, Colorado State University, Fort Collins, CO, USA

Zachary M. Burcham, Aeriel D. Belk, Alexandra Emmons, Victoria Nieciecki & Jessica L. Metcalf

Department of Microbiology, University of Tennessee, Knoxville, TN, USA

Zachary M. Burcham

Department of Animal Sciences, Auburn University, Auburn, AL, USA

Aeriel D. Belk

Department of Soil and Crop Sciences, Colorado State University, Fort Collins, CO, USA

Bridget B. McGivern, Michael Shaffer & Kelly C. Wrighton

Collaborative Mass Spectrometry Innovation Center, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, San Diego, CA, USA

Amina Bouslimani, Morgan Panitchpakdi, Kelly C. Weldon & Pieter C. Dorrestein

Department of Chemical and Biological Engineering, Colorado State University, Fort Collins, CO, USA

Parsa Ghadermazi & Siu Hung Joshua Chan

Department of Pediatrics, University of California San Diego, La Jolla, California, USA

Cameron Martino, Qiyun Zhu, Greg C. Humphry, Gail Ackermann, Daniel McDonald & Rob Knight

Center for Studies in Physics and Biology, Rockefeller University, New York, NY, USA

Liat Shenhav

Institute for Systems Genetics, New York Grossman School of Medicine, New York University, New York, NY, USA

Department of Computer Science, New York University, New York, NY, USA

Department of Biostatistics and Bioinformatics, Duke University, Durham, NC, USA

Anru R. Zhang & Pixu Shi

Department of Computer Science, Duke University, Durham, NC, USA

Anru R. Zhang

Graduate Program in Cell and Molecular Biology, Colorado State University, Fort Collins, CO, USA

Heather L. Deel, Victoria Nieciecki & Jessica L. Metcalf

School of Food Science and Technology, Nanchang University, Nanchang, Jiangxi, China

Zhenjiang Zech Xu

School of Life Sciences, Arizona State University, Tempe, AZ, USA

Center for Fundamental and Applied Microbiomics, Arizona State University, Tempe, AZ, USA

Department of Computer Science and Engineering, University of California San Diego, La Jolla, CA, USA

Kalen Cantrell & Rob Knight

Department of Computer Science, Colorado State University, Fort Collins, CO, USA

Asa Ben-Hur

U.S. Geological Survey, Southwest Biological Science Center, Moab, UT, USA

Sasha C. Reed

Forensic Investigation Research Station, Colorado Mesa University, Grand Junction, CO, USA

Melissa Connor

Forensic Anthropology Center, Department of Anthropology, University of Tennessee, Knoxville, TN, USA

Derek Boyd, Jake Smith, Jenna M. S. Watson, Giovanna Vidoli & Dawnie Steadman

Department of Social, Cultural, and Justice Studies, University of Tennessee at Chattanooga, Chattanooga, TN, USA

Mid-America College of Funeral Service, Jeffersonville, IN, USA

Department of Biological Sciences, Sam Houston State University, Huntsville, TX, USA

Aaron M. Lynne & Sibyl Bucheli

Laboratory of Forensic Taphonomy, Forensic Sciences Unit, School of Natural Sciences and Mathematics, Chaminade University of Honolulu, Honolulu, HI, USA

David O. Carter

Center for Microbiome Innovation, University of California San Diego, La Jolla, CA, USA

Department of Bioengineering, University of California San Diego, La Jolla, CA, USA

Humans and the Microbiome Program, Canadian Institute for Advanced Research, Toronto, Ontario, Canada

Jessica L. Metcalf

You can also search for this author in PubMed   Google Scholar

Contributions

Z.M.B., D.O.C., R.K., K. C. Wrighton and J.L.M. conceptualized the project. Z.M.B., A.D.B., B.B.M., A.B., C.M., H.L.D., M.P., K. C. Weldon, G.C.H., G.A., M.C., D.B., J.S., G.V., D.S., A.M.L., S.B., P.C.D., K. C. Wrighton, D.O.C., R.K. and J.L.M. contributed to data curation. Z.M.B., A.D.B., B.B.M., P.G., C.M., L.S., A.R.Z., P.S., A.E., H.L.D., V.N., M.S., K.C. and D.M. conducted formal analysis. K. C. Wrighton, D.O.C., R.K. and J.L.M. acquired funding. A.B., M.P., K. C. Weldon, M.C., D.B., J.S., J.M.S.W., G.V., D.S., A.M.L. and S.B. contributed to project investigation. Z.M.B., A.D.B., B.B.M., A.B., P.G., C.M., L.S., A.R.Z., P.S., Z.Z.X., V.N., Q.Z., M.S., M.P., K. C. Weldon, K.C., A.B.-H., S.H.J.C., M.C., D.B., J.S., G.V., D.S., A.M.L., S.B., P.C.D., K. C. Wrighton, D.O.C., R.K. and J.L.M. developed the methodology. Z.M.B., M.C., G.V., D.S., A.M.L., S.B., P.C.D., K. C. Wrighton, D.O.C., R.K. and J.L.M. administered the project. S.H.J.C., M.C., G.V., D.S., A.M.L., S.B., P.C.D., K. C. Wrighton, D.O.C. and R.K. provided resources. Z.M.B., A.D.B., B.B.M., P.G., C.M., L.S., A.R.Z., P.S., Z.Z.X., M.S., K.C., A.B.-H., D.M. and P.C.D. developed software. S.H.J.C., M.C., G.V., D.S., A.M.L., S.B., P.C.D., K. C. Wrighton, D.O.C. and R.K. supervised the project. Z.M.B., A.D.B., B.B.M., P.G., C.M., M.C., G.V., D.S., A.M.L., S.B., P.C.D., K. C. Wrighton, R.K. and J.L.M. conducted data validation. Z.M.B., A.D.B., B.B.M., P.G., C.M., A.E. and S.C.R. worked on visualization. Z.M.B., A.D.B., A.E., B.B.M., S.C.R., D.O.C. and J.L.M. wrote the original draft. Z.M.B., A.D.B., B.B.M., P.G., C.M., H.L.D., S.C.R., D.M., M.C., S.B., P.C.D., K. C. Wrighton, D.O.C., R.K. and J.L.M. reviewed and edited the manuscript.

Corresponding author

Correspondence to Jessica L. Metcalf .

Ethics declarations

Competing interests.

P.C.D. consulted in 2023 for DSM animal health, is a consultant and holds equity in Sirenas and Cybele Microbiome, and is founder and scientific advisor and has equity in Ometa Labs LLC, Arome and Enveda (with approval by UC San Diego). R.K. is affiliated with Gencirq (stock and SAB member), DayTwo (consultant and SAB member), Cybele (stock and consultant), Biomesense (stock, consultant, SAB member), Micronoma (stock, SAB member, co-founder) and Biota (stock, co-founder). The other authors declare no competing interests.

Peer review

Peer review information.

Nature Microbiology thanks Anna Heintz-Buschart, Michael Strickland and Aleksej Zelezniak for their contribution to the peer review of this work.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Extended data fig. 1 study information..

Average a ) temperature data and b ) total precipitation per location over experiment with cadaver placement dates. Temperature data was collected from local weather stations reported to the National Centers for Environmental Information. Total monthly precipitation data was collected from Weather Underground. The vertical line represents the date of placement and line color denotes the season the body placement is considered to have been placed. c ) Upset plot illustrating the intersections between sample and omic types after extractions, processing and quality filtering that were used for further analyses. MetaG = metagenomics, Metab = metabolomics, 18S = 18S rRNA amplicon, and 16S = 16S rRNA amplicon.

Extended Data Fig. 2 Metabolome Comparison.

Principal coordinate analysis (PCoA) of a ) Jaccard and b ) Bray-Curtis distances of all unique metabolites and all metabolomic samples show cadaver skin and cadaver-associated soil are significantly different community profiles. n = 1503 biologically independent samples. Significance was determined by PERMANOVA (permutations = 999). Van Krevelen diagram showed a strong presence of lipid-like, protein-like, and lignin-like classes within c ) cadaver-associated soils and d ) cadaver skin. Metabolites that matched database chemical formulas or had a significantly predicted chemical formula were assigned a Van Krevelen organic compound classification by their hydrogen:carbon and oxygen:carbon molar ratios. Colors correspond to organic compound classification. Nominal oxidation state of carbon (NOSC) scores for cadaver-associated e ) soil and f ) cadaver skin metabolites with assigned chemical formulas show significant decrease of thermodynamic favorability at all geographical locations over decomposition time measured by accumulated degree days (ADD). Soil: ARF n = 251, STAFS n = 250, and FIRS n = 245 biologically independent samples. Skin: ARF n = 250, STAFS n = 249, and FIRS n = 249 biologically independent samples. Data are presented as mean values +/− 95% CI. Significance measured with linear mixed-effects models within each location and adding a random intercept for cadavers with two-tailed ANOVA and no multiple comparison adjustments. g ) Lipid-like metabolites show an increased abundance in cadaver-associated soils over decomposition measured by accumulated degree days (ADD) and significantly increase in temperate soils. h ) Protein-like metabolites are less abundant than lipid-like metabolites in cadaver-associated soils over decomposition measured by accumulated degree days (ADD) and significantly decrease in STAFS soil. ARF n = 251, STAFS n = 250, and FIRS n = 245 biologically independent samples. Data are presented as mean values +/− 95% CI. Significance measured with linear mixed-effects models within each location and adding a random intercept for cadavers with two-tailed ANOVA and no multiple comparison adjustments. Metabolite abundance normalized by center log ratio transformation.

Extended Data Fig. 3 Community Assembly.

Sankey diagram of the a ) 257 99% dereplicated, medium to high quality MAGs with Genome Taxonomy Database classifications and b ) the average MAG abundances (given as transcript per million, TPM) at each decomposition stage within each location. Proteobacteria and Bacteroidota representation increases with decomposition while Actinobacteria representation decreases at each location. This MAG set encompassed novel bacterial orders (n=3), families (n=9), genera (n=28), and species (n=158). Proteobacteria is the highest represented phylum. c ) Spearman correlation of the maximum ATP per C-mol for lipids, carbohydrates, and amino acids over ADD at each location represented by circle size. Metabolism efficiency is correlated with ADD in temperate climates. ARF n = 212, STAFS n = 198, and FIRS n = 158 biologically independent samples. Significance measured with linear mixed-effects models within each location and adding a random intercept for cadavers and denoted as p<0.05 (*), p<0.01 (**), and p<0.001 (***). ARF: Amino Acids p = <2e-16, STAFS: Amino Acids p = 1.18e-06, and Carbohydrate p = 4.22e-04. d ) The amino acid metabolism efficiency of the total community that can be attributed to O. alkaliphila and e ) the carbohydrate metabolism efficiency of the total community that can be attributed to C. intestinavium increase over decomposition at temperate locations as a product of the genome’s metabolism efficiency and relative abundance. Data plotted with loess regression as mean values +/− 95% CI. ARF n = 212, STAFS n = 198, and FIRS n = 158 biologically independent samples. f ) Pairwise comparisons to obtain beta nearest taxon index (βNTI) values focused on successional assembly trends by comparing initial non-decomposition soil to early decomposition soil then early to active, etc. (PL = placement, EA = early, AC = active, AD = advanced) in the 16S rRNA amplicon dataset. Relative abundance of assembly forces reveals that heterogeneous selection (βNTI > +2) pressure increases and homogenous selection (βNTI < -2) decreases over decomposition. Stochastic forces are a constant driver of community assembly (+2 > βNTI > -2). g ) Predicted metabolic competition from metagenome-assembled genomes are site-specific and significantly altered over decomposition. STAFS: early-active p = 3.42e-11, early-advanced p = 1.23e-11, active-advanced p = 7.85-41, FIRS: early-active p = 0.042. h ) Predicted metabolic cooperation and competition from metagenome-assembled genomes randomly subsampled into 20-member communities within each site and decomposition serves as a null model comparison signifying the importance of MAG co-occurrence. ARF n = 201, STAFS n = 188, and FIRS n = 151 biologically independent samples. The lower and upper hinges of the boxplot correspond to the first and third quartiles (the 25th and 75th percentiles). The upper whisker extends from the hinge to the largest value no further than 1.5 * IQR from the hinge, and the lower whisker extends from the hinge to the smallest value at most 1.5 * IQR of the hinge. The center of the boxplot is represented by the median. Significance measured with Dunn Kruskal-Wallis H-test with multiple comparison p-values adjusted with the Benjamini-Hochberg method as denoted by p<0.05 (*), p<0.01 (**), and p<0.001 (***).

Extended Data Fig. 4 Multi-omic Integration.

a ) ASV richness comparison between decomposition soil and control soil over the decomposition time frame reveals that bacterial richness decreases significantly at temperate locations. ARF n = 414, STAFS n = 316, and FIRS n = 310 biologically independent samples. Significance measured with linear mixed-effects models within each location and adding a random intercept for cadavers with two-tailed ANOVA and no multiple comparison adjustments. ARF and STAFS richness p = <2e-16. Denoted as p<0.05 (*), p<0.01 (**), and p<0.001 (***). b ) Multi-omic joint-RPCA shows that microbial community ecology is impacted by season and geographical location. Multi-omic Joint-RPCA incorporates soil 16S rRNA, 18S rRNA, metabolomic, and metagenome-assembled genome data. All data types used the same n = 374 biologically independent samples. Multi-omics joint-RPCA principal component scores show that c ) facility variation is primarily explained by principal component 3 (PC3) and PC4, d ) decomposition stage is primarily explained by PC2, e ) season is primarily explained by PC1, and f ) climate is primarily explained by PC3 and PC4 as described by the least overlap of PC values between groups. g ) PC2 from the multi-omics joint-RPCA scores for each geographical location over decomposition stages shows the temperate climate locations are the most dynamic in their microbial ecology. Multi-omic Joint-RPCA incorporates soil 16S rRNA, 18S rRNA, metabolomic, and metagenome-assembled genome data. All data types used the same n = 374 biologically independent samples. Data in panel g are presented as mean values +/− 95% CI.

Extended Data Fig. 5 Universal Initial Non-Decomposition And Early Decomposition Soil Network.

Top 20% of correlations between selected nodes for the universal initial non-decomposition and early decomposition soil log-ratio signal in Joint-RPCA PC2 visualized in co-occurrences network. All data types used the same n = 374 biologically independent samples.

Extended Data Fig. 6 Decomposer ASVs Placed in Current Databases.

Phylogenetic tree representing ASVs associated with the key decomposer nodes from the network placed along within the top 50 most abundant ASVs taken from AGP gut, AGP skin, EMP soil, and EMP host-associated datasets demonstrates key decomposers are largely phylogenetically unique. Innermost ring represents decomposer placement while outer rings represent AGP and EMP ASVs, for which bar height represents ASV rank prevalence within each environment. AGP and EMP ASVs were ranked according to the number of samples they were found in each environment. A lack of bars represents that the ASV was not present within the dataset. Decomposer ASVs are numbered clockwise with full taxonomy available in Supplementary Table 27 .

Extended Data Fig. 7 Important Features for 16S rRNA Random Forest Models.

The 20 most important SILVA level-7 taxa as determined in the 16S rRNA random forest regression models for predicting postmortem interval shows that many of the same taxa appear important for model prediction within all sample types, but some differences do emerge.

Extended Data Fig. 8 Longitudinal Abundances of Important Features.

The 6 most important SILVA level-7 taxa as determined in the 16S rRNA data from the a ) skin of the face, b ) skin of the hip, c ) soil associated with the hip, and d ) soil associated with the face for random forest regression models for predicting postmortem interval. Data plotted by the taxa and the normalized abundance change over ADD at each geographic location. Data plotted with loess regression and 16S rRNA soil face, soil hip, skin face, and skin hip datasets contain n = 600, 616, 588, and 500 biologically independent samples, respectively. Data are presented as mean values +/− 95% CI.

Extended Data Fig. 9 16S rRNA Random Forest Model Validation.

a ) Total body scores (TBS) used to train a random forest model for prediction of PMI (ADD) shows that TBS scores can predict PMI relatively accurately based on a low MAE but have higher variability in their predictions as represented by a higher residual value than microbiome-based models. Models built from 16S rRNA data using SILVA level-7 taxa from the skin and soil associated with the hip were validated with b ) an independent test set of samples that were collected from cadavers at locations and climates not represented in our model and c ) the same data where samples were given randomly assigned ADDs within the range of true ADDs to serve as a null model. Significance measured with linear mixed-effects models within each location and adding a random intercept for cadavers with two-tailed ANOVA and no multiple comparison adjustments. Data are presented as mean values +/− 95% CI.

Extended Data Fig. 10 Diversity Comparison between 16S rRNA and Metagenomic Data.

PCoA ordination plots of Bray-Curtis dissimilarity matrices calculated from paired rarefied 16S rRNA feature abundances (left) and TPM-normalized MAG abundances (right) from the soil adjacent to the hip. Procrustes/PROTEST and mantel tests were performed between the PCoA ordinances and distance matrices, respectively. n = 480 biologically independent samples, respectively.

Supplementary information

Supplementary information.

Legends for Supplementary Tables 1–9, 14–16 and 25–39. Supplementary Tables 10–13 and 17–24, and Text.

Reporting Summary

Supplementary tables.

Supplementary Table 1. Sample metadata. Table includes data taken during intake and over the course of the study. Table 2. ANCOM-BC differential abundance analysis results of cadaver skin metabolite log-ratio change over decomposition stages. Initial day 0 samples were used as the reference level and the intercept. Results include log-ratio changes of day 0 metabolites to early, active and advanced decomposition stages, P values, Holm–Bonferroni-corrected P values ( Q values), standard errors and W values. Table 3. ANCOM-BC differential abundance analysis results of cadaver-associated soil metabolite log-ratio change over decomposition stages. Initial day 0 samples were used as the reference level and the intercept. Results include log-ratio changes of day 0 metabolites to early, active and advanced decomposition stages, P values, Holm–Bonferroni-corrected P values ( Q values), standard errors and W values. Table 4. List of samples used to generate shotgun metagenomic data. Table 5. Assembly statistics and GTDB taxonomic classification of genomic bins (metagenome-assembled genomes; MAGs) co-assembled from the metagenomic samples. Table includes completeness and contamination of each MAG. Table 6. TPM-normalized count abundance of MAGs within metagenomic samples. Table 7. Linear mixed-effects model statistics for testing response variable change of ATP per C-mol amino acids calculated from metagenomic data over ADD at each facility and a random intercept for each individual body to account for repeated measures to test whether the metabolism efficacy shifts within each facility. Formula: ‘ATPm ≈ ADD + (1|body ID)’. Table 8. Linear mixed-effects model statistics for testing response variable change of ATP per C-mol carbohydrates calculated from metagenomic data over ADD at each facility and a random intercept for each individual body to account for repeated measures to test whether the metabolism efficacy shifts within each facility. Formula: ‘ATPm ≈ ADD + (1|body ITable 9. Linear mixed-effects model statistics for testing response variable change of ATP per C-mol lipids calculated from metagenomic data over ADD at each facility and a random intercept for each individual body to account for repeated measures to test whether the metabolism efficacy shifts within each facility. Formula: ‘ATPm ≈ ADD + (1|body ID)’. Table 14. Number of predicted exchanges for cross-fed compounds at each facility during late decomposition. Late decomposition was defined as the advanced decomposition stage at STAFS and ARF and the active decomposition stage at FIRS. Table 15. Linear mixed-effects model statistics for testing response variable change of Generalized UniFrac PC1 distances calculated from 16S rRNA gene data over ADD at each facility with sampling site (that is, soil adjacent to hip vs soil control) as an independent variable (fixed effect) and a random intercept for each individual body to account for repeated measures. The models measure the sampling site and ADD variables individually and the interaction between the variables. The interaction between the variables was used to test whether the sampling sites respond differently to decomposition. Formula: ‘diversity metric ≈ ADD × sampling site + (1|body ID)’. Table 16. Linear mixed-effects model statistics for testing response variable change of ASV richness calculated from 16S rRNA gene data over ADD at each facility with sampling site (that is, soil adjacent to hip vs soil control) as an independent variable (fixed effect) and a random intercept for each individual body to account for repeated measures. The models measure the sampling site and ADD variables individually and the interaction between the variables. The interaction between the variables was used to test whether the sampling sites respond differently to decomposition. Formula: ‘diversity metric ≈ ADD × sampling site + (1|body ID)’. Table 25. Joint-RPCA PC2 correlations calculated between network feature nodes that correspond with late (that is, active and advanced) decomposition soil. Table 26. Joint-RPCA PC2 correlations calculated between network feature nodes in initial, non-decomposition and early decomposition soil. Table 27. 16S rRNA gene ASVs assigned to the same taxonomy as decomposer network taxa. Table includes the phylogenetic tree labels in Fig. 4e, 150-bp-long ASVs and trimmed 100-bp-long ASVs used to explore ASV presence in other studies. Table 28. Presence of universal decomposers in possible human and terrestrial source environments in a few other studies. Table shows the average relative abundance of each decomposer ASV across each sample type. Average relative abundances were then summed for each decomposer genus. Table 29. Cross-feeding statistics for MAGs predicted as cross-feeders during late decomposition. Table includes GTDB taxonomic classification, number of reactions each MAG was considered the compound receiver and/or donor, and the percent responsible for all donations and acceptances during late decomposition. Late decomposition was defined as the advanced decomposition stage at STAFS and ARF and the active decomposition stage at FIRS. Table 30. Cross-feeding exchanges for Oblitimonas alkaliphila during late decomposition. Oblitimonas alkaliphila was not a predicted cross-feeder at FIRS during this timeframe. Table includes MAG ID and taxonomic classification of genomes involved in exchange, compounds exchanged and computed interaction metrics. Table 31. Cross-feeding exchanges for l -arginine or ornithine during late decomposition. Table includes MAG ID and taxonomic classification of genomes involved in exchange, compounds exchanged and computed interaction metrics. Table 32. Model validation results from predicting an independent test set of samples using the 16S rRNA gene at the SILVA database level-7 taxonomic rank random forest regression models for the skin of the hip and soil adjacent to the hip. Errors are represented by MAE in ADD. Table 33. Presence of universal decomposers in a few other studies focused on mammalian decomposition environments. A search for the 35 universal PMI decomposer ASVs was conducted within each dataset. The relative abundance of each decomposer ASV was first averaged across all samples within a specific metadata category. The average relative abundances were then summed across each decomposer genus. Prevalence tables were constructed by summing the number of samples across a specific metadata category in which each universal decomposer ASV was present. Table 34. The average ADD per calendar day calculated for each cadaver at each facility. The average ADD per calendar day was calculated by dividing the final maximum ADD values by the total number of days (that is, 21). The average ADD per day was calculated for each cadaver, season and facility, each climate type and as a study-wide average. Table 35. The average ADD per calendar day calculated for each cadaver at each facility for the independent test set. The average ADD per calendar day was calculated by dividing the final maximum ADD values by the total number of sampling days. The average ADD per day was calculated for each cadaver, facility and as a study-wide average. Table 36. Metabolite identification information for metabolites that had a predicted chemical formula or matched to a compound in the database library. When available, chemical formulas in the database library took precedence over predicted chemical formulas for calculating NOSC and major biochemical classes based on the molar H:C and O:C ratios. Table 37. Soil metabolite feature table normalized with sum normalization then scaled with pareto scaling. Table includes chemical formulas and major biochemical classes based on the molar H:C and O:C ratios. Table 38. Skin metabolite feature table normalized with sum normalization then scaled with pareto scaling. Table includes chemical formulas and major biochemical classes based on the molar H:C and O:C ratios. Table 39. Sample metadata for the machine learning independent test set. Table includes data taken during intake and over the course of the study.

Source Data for Figs. 1–6, Extended Data Figs. 1–6 and Extended Data Fig. 9

SD for Fig. 1. Sample type counts and sample metadata. SD for Fig. 2. ATP per C-mol for each substrate by sample and pairwise beta-NTI calculations. SD for Fig. 3. SMETANA MIP and MRO score calculations, predicted cross-fed metabolites, Faith’s PD calculations and joint-RPCA distance matrix/ordination. SD for Fig. 4. Joint-RPCA distance matrix/ordination and multi-omic log ratios. SD for Fig. 5. Late decomposition multi-omic correlations. SD for Fig. 6. Random forest predictions, 16S rRNA model important features and 16S rRNA SILVA-L7 feature table. SD for ED Fig. 1. Site weather data. SD for ED Fig. 2. Metabolite feature table, chemical formulas and Van Krevelen metabolite classifications. SD for ED Fig. 3. MAG taxonomy and feature table, amino acid and carbohydrate ATP per C-mol per MAG and sample. SD for ED Fig. 4. 16S rRNA calculated richness. SD for ED Fig. 5. Initial/early decomposition multi-omic correlations. SD for ED Fig. 6. Top rank taxa for phylogenetic tree comparing ASVs found during decomposition and in the EMP and AGP datasets. SD for ED Fig. 9. 16S rRNA random forest validation predictions

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ .

Reprints and permissions

About this article

Cite this article.

Burcham, Z.M., Belk, A.D., McGivern, B.B. et al. A conserved interdomain microbial network underpins cadaver decomposition despite environmental variables. Nat Microbiol (2024). https://doi.org/10.1038/s41564-023-01580-y

Download citation

Received : 28 June 2023

Accepted : 08 December 2023

Published : 12 February 2024

DOI : https://doi.org/10.1038/s41564-023-01580-y

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

This article is cited by

Decomposer communities are universal in death.

  • Michael S. Strickland
  • Laurel Lynch

Nature Microbiology (2024)

Quick links

  • Explore articles by subject
  • Guide to authors
  • Editorial policies

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

how write reference research paper

COMMENTS

  1. References in Research

    Definition: References in research are a list of sources that a researcher has consulted or cited while conducting their study. They are an essential component of any academic work, including research papers, theses, dissertations, and other scholarly publications. Types of References

  2. How To Write Your References Quickly And Easily

    In general, a reference will include authors' names and initials, the title of the article, name of the journal, volume and issue, date, page numbers and DOI. On ScienceDirect, articles are linked to their original source (if also published on ScienceDirect) or to their Scopus record, so including the DOI can help link to the correct article.

  3. How to Cite Sources

    Simply enter the URL, DOI, or title, and we'll generate an accurate, correctly formatted citation. Generate accurate citations with Scribbr Instantly correct all language mistakes in your text Be assured that you'll submit flawless writing. Upload your document to correct all your mistakes. Table of contents When do you need to cite sources?

  4. How to write references in research papers| Researcher.Life

    Whereas citations merely point us to sources in research papers, references describe those sources in sufficient detail for readers (1) to know the title of each source, who is responsible for its content, and when it was published; (2) to look up those sources; and (3) to obtain the documents in question if required.

  5. How To Cite a Research Paper in 2024: Citation Styles Guide

    IEEE Style Citation Guide The main reason for citing references properly is to avoid intellectual dishonesty (Bast & Samuels, 2008). Presenting ideas of other scholars without proper research paper citation goes against scientific ethics (Gross, 2016). While this is not the highest of ethical requirements, it is simply basic decency.

  6. How to Cite in APA Format (7th edition)

    An APA in-text citation consists of the author's last name and the year of publication (also known as the author-date system). If you're citing a specific part of a source, you should also include a locator such as a page number or timestamp. For example: (Smith, 2020, p. 170). Parenthetical vs. narrative citation

  7. 5 Ways to Cite a Research Paper

    When writing a paper for a research project, you may need to cite a research paper you used as a reference. The basic information included in your citation will be the same across all styles.

  8. 13.3 Creating a References Section

    1. Include the heading References, centered at the top of the page. The heading should not be boldfaced, italicized, or underlined. 2. Use double-spaced type throughout the references section, as in the body of your paper. 3.

  9. How to Write a Research Paper

    How to Write a Research Paper | A Beginner's Guide A research paper is a piece of academic writing that provides analysis, interpretation, and argument based on in-depth independent research.

  10. A Quick Guide to Referencing

    In-text citations are quick references to your sources. In Harvard referencing, you use the author's surname and the date of publication in brackets. Up to three authors are included in a Harvard in-text citation. If the source has more than three authors, include the first author followed by ' et al. '.

  11. Reference List: Basic Rules

    Reference List: Basic Rules. This resourse, revised according to the 7 th edition APA Publication Manual, offers basic guidelines for formatting the reference list at the end of a standard APA research paper. Most sources follow fairly straightforward rules. However, because sources obtained from academic journals carry special weight in research writing, these sources are subject to special ...

  12. A Quick Guide to Harvard Referencing

    When you cite a source with up to three authors, cite all authors' names. For four or more authors, list only the first name, followed by ' et al. ': Number of authors. In-text citation example. 1 author. (Davis, 2019) 2 authors. (Davis and Barrett, 2019) 3 authors.

  13. Reference List: Common Reference List Examples

    For example, you are citing study notes titled "Health Effects of Exposure to Forest Fires," but you do not know the author's name, your reference entry will look like this: Health effects of exposure to forest fires [Lecture notes]. (2005). Walden University Canvas. https://waldenu.instructure.com.

  14. How To Cite a Research Paper (With APA Citation Examples)

    Here are the general rules to follow when citing a research paper in an APA style format: Book: Last Name, First Initial. (Year of Publication). Title of the work. Publisher. Example: Thompson, S. (1982). The Year of the Wolf. Preston and Buchanan. Magazine: Last Name, First Initial. (Year, Month of Publication). Article title.

  15. Formatting References for Scientific Manuscripts

    The advantage of having a constant style within a journal is two-fold, apart from an esthetic appearance of references across all articles published by the journal. Ease of reading the references at the end of each article and ease of finding reference part by the reader if he/she is used to the format and plans to look up the reference.

  16. How to Write References and Cite Sources in a Research Paper

    How to Write References and Cite Sources in a Research Paper Last update date: December 28, 2023 5 min read Table of contents 1 Why Referencing and Citation Matter 1.1 Academic Integrity 1.2 Avoiding Plagiarism 1.3 Building Credibility 1.4 Facilitating Further Research 2 Choosing the Right Citation Style 2.1 APA (American Psychological Association)

  17. How To Write References for Academic & Scientific Research Papers

    1. The in-text citation should contain the last name of the author (or last names of the authors if there is more than one) who wrote the article, book or other document followed by the document's date of publication. This information most frequently appears in parentheses immediately after the statement related to the paper, as in this example:

  18. How to Cite Research Paper

    How to Cite Research Paper There are several formats that are used to cite a research paper. Follow the guide for the Citation of a Research Paper: MLA Format Books Last Name, First Name. Title of Book. Publisher, Year of Publication. Example: Smith, John. The History of the World. Penguin Press, 2010. Journal Article Last Name, First Name.

  19. How to write references in research paper

    How to write references in research paper and how to get references for a research paper and how to make references in a research paper, how to put references in a research...

  20. Research Paper

    Definition: Research Paper is a written document that presents the author's original research, analysis, and interpretation of a specific topic or issue. It is typically based on Empirical Evidence, and may involve qualitative or quantitative research methods, or a combination of both. The purpose of a research paper is to contribute new ...

  21. Free Research Paper Template (Word Doc & PDF)

    If you're preparing to write an academic research paper, our free research paper template is the perfect starting point. In the template, we cover every section step by step, with clear, straightforward explanations and examples.. The template's structure is based on the tried and trusted best-practice format for formal academic research papers. The template structure reflects the overall ...

  22. Getting Help with Your Paper

    Email us. Replies sent within 24 hours (except holidays and weekends). Schedule an appointment with us. Best for in-depth assistance with complex research assignments. We can take phone calls or set up Zoom meetings.

  23. How to Write a Term Paper: 8 Expert Tips for Academic Success 2024

    5. Writing the Draft. With your outline in hand, it's time to start writing. The introduction should hook the reader, present your thesis statement, and outline the structure of your paper. Each body paragraph should focus on a single idea or piece of evidence, supporting your thesis.

  24. Research Paper Format

    Formatting an APA paper. The main guidelines for formatting a paper in APA Style are as follows: Use a standard font like 12 pt Times New Roman or 11 pt Arial. Set 1 inch page margins. Apply double line spacing. If submitting for publication, insert a APA running head on every page. Indent every new paragraph ½ inch.

  25. Finding Sources for Your Paper

    When you click "Define Your Search," you are presented with options you must select before you can type your search terms: Books (print + ebooks) will search the OneSearch system. Articles will search the OneSearch system for articles in journals, newspapers, and magazines.. Videos will search the OneSearch system for streaming videos and DVDs. Books + Articles + Videos will search OneSearch ...

  26. Researching the White Paper

    Researching the White Paper: The process of researching and composing a white paper shares some similarities with the kind of research and writing one does for a high school or college research paper. What's important for writers of white papers to grasp, however, is how much this genre differs from a research paper.

  27. The abortion pill case on its way to the Supreme Court cites a

    A research paper that raises questions about the safety of abortion has been retracted. The research is cited in a federal judge's ruling about the abortion pill mifepristone. Accessibility links

  28. A conserved interdomain microbial network underpins cadaver ...

    a-c, Lipid (a), carbohydrate (b) and amino acid (c) metabolism efficiency as determined by the maximum ATP per C-mol of substrate that can be obtained from each community, plotted against the ...