Last updated: April 2026 · 7 min read · Audience: Authors, students, early-career researchers · Reading level: Introductory
Quick answer. To cite a source in a research paper: (1) follow the citation style required by your target journal — APA, MLA, Harvard, or Chicago — (2) include an in-text citation every time you use a source, and (3) list every cited work in a reference list at the end of the paper. Use a reference manager (Zotero, Mendeley, EndNote) configured to the journal's style. This eliminates 90% of citation errors.
This guide explains how to cite sources in academic writing, when to cite, the differences between the major citation styles, and how to handle journal articles, books, websites, and AI-generated content.
When you must cite a source
Cite a source whenever you use someone else's idea, finding, or wording — whether you quote it directly, paraphrase it, or summarise it. The four common situations are:
- Direct quotation — the source's words appear verbatim, surrounded by quotation marks, with citation and page number.
- Paraphrasing — you restate the source's idea in your own words. Citation is required even when no words are reused.
- Summarising — you condense a longer argument into your own brief description. Citation is required.
- Using data, figures, or tables — any chart, statistic, or visual reproduced or adapted from another source must be cited and (for direct reproduction) requires permission.
Common knowledge does not require citation — facts that any educated reader would know without consulting a source. When in doubt, cite. Failing to cite is plagiarism, even when unintentional. Read more on avoiding plagiarism in research.
The four major citation styles compared
Most academic journals use one of four citation styles. The choice is determined by the journal — always check author guidelines before drafting your reference list.
APA (American Psychological Association)
Used in psychology, education, and most social sciences. Author–date format. Reference list ordered alphabetically by author surname.
In-text: (Smith, 2024) or Smith (2024) argued that…
Reference: Smith, J. (2024). Title of article. Journal Name, 12(3), 45–67. https://doi.org/10.1234/example
MLA (Modern Language Association)
Used in humanities — literature, language studies, cultural studies. Author–page format. Reference list called "Works Cited."
In-text: (Smith 45) or Smith argues that … (45).
Reference: Smith, John. "Title of Article." Journal Name, vol. 12, no. 3, 2024, pp. 45–67.
Harvard
Common in UK and Australian universities, especially in business, economics, and social sciences. Author–date, similar to APA but with minor punctuation differences. Many institutions use a slightly different "house style" — confirm with your supervisor or journal.
Chicago / Turabian
Used in history, theology, and some sciences. Two systems: Notes-Bibliography (footnotes plus a bibliography) and Author-Date (similar to APA). Choose based on the journal's preference.
How to cite a journal article
Always include the DOI when one exists — even for print-only articles. DOIs are permanent identifiers that ensure your reference remains accessible even if the publisher changes the article URL.
APA 7 example:
Patel, R., & Chen, L. (2024). Affordable open access publishing in low-income countries. Journal of Scholarly Publishing, 18(4), 112–128. https://doi.org/10.1234/jsp.2024.018
How to cite a book
APA 7:
Davies, M. (2023). Research methodology in the social sciences (3rd ed.). Routledge.
MLA 9:
Davies, Margaret. Research Methodology in the Social Sciences. 3rd ed., Routledge, 2023.
How to cite a website
Include author (if available), year, page title, site name, and URL. Use (n.d.) when no date is provided.
APA 7:
EP Journals Group. (2024, March 12). Open access publishing explained. https://www.ep-journals.org/guides/understanding-open-access-publishing
In-text citations versus the reference list
Both are required. The in-text citation gives readers a quick pointer (author and year, or author and page) so they can locate the full reference at the end. The reference list provides the complete bibliographic detail. Every in-text citation must appear in the reference list, and every reference list entry must be cited at least once in the text. Mismatches between the two are the most common cause of desk rejection on formatting grounds.
Use a citation manager
Manual citation is error-prone and time-consuming. Citation managers automate the formatting and let you switch between styles instantly. The three most widely used:
- Zotero — free, open-source, recommended for most authors. Browser plugin captures citation data from publisher pages.
- Mendeley — free, owned by Elsevier. Good integration with Word and LaTeX.
- EndNote — paid, common in research-intensive institutions. Powerful but with a steeper learning curve.
All three integrate with Microsoft Word, Google Docs, and LaTeX. Configure the manager to use your target journal's style before drafting, and you will rarely need to format a citation by hand.
Citing AI-generated content (ChatGPT and similar)
Citation rules for AI tools are still evolving. APA 7 currently recommends citing the AI tool as the author, including the version, date of access, and prompt used. However, most peer-reviewed journals will not accept AI-generated text as a primary source. Use AI tools for brainstorming and drafting, never as a substitute for verified scholarly references — large language models frequently fabricate citations that look plausible but do not exist.
Common citation mistakes (and how to avoid them)
- Missing DOIs — always check whether a DOI exists. Most journal articles published since 2000 have one.
- Inconsistent author name format — APA uses "Last, F.M."; MLA uses "Last, First Middle." Mixing styles within a reference list is a red flag for reviewers.
- Citation–reference list mismatch — every in-text citation must have a matching reference, and vice versa. Do a final cross-check before submission.
- Wrong style for the journal — verify the target journal's required style in the author guidelines before drafting. Switching styles late is painful.
Further reading
Frequently asked questions
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Related reading and next steps
- Submission portal — Submit a manuscript through the central form
- Journals list — Six peer-reviewed journals across disciplines
- Avoiding plagiarism
- Writing a research paper step by step
- Structured vs unstructured
- Publishing in medical research
Editorial enquiries
Questions about this guide or about preparing a manuscript for submission may be directed to the editorial office. Where a query relates to a specific journal in the portfolio, please indicate the journal abbreviation in your message.
Email: editor@ep-journals.org