How to Cite Sources Properly: Format, Examples and Common Errors

To cite sources properly, give every borrowed idea two matching pieces: a short in-text citation where you use the source, and a full reference entry that lets a reader find it. Cite sources correctly by making the two agree exactly: same author spelling, same year, and one entry per citation. This guide shows the structure with the APA 7th edition, the style most often required in the social and health sciences, then notes how MLA and Chicago differ.

The format: what a reference entry contains

A complete entry has the same named elements in the same order. APA’s own reference guide gives this template for a journal article:

Author, A. A., & Author, B. B. (Year). Title of the article. Name of the Periodical, volume(issue), #–#. https://doi.org/xxxx

• Author: last name first, then initials, with a space between initials.
• Year: in parentheses, followed by a period.
• Article title: capitalise only the first word (and the first word after a colon in a two-part title) and proper nouns; do not italicise.
• Periodical name: capitalise all major words and italicise it; the volume number is italic too, while the issue number in parentheses is not, with no space before the parenthesis.
• Pages: separated by an en dash with no spaces.
• DOI: include one for every work that has it, written as a https://doi.org/ link with no period after it.

For a book, the pattern is Author, A. A. (Year). Title of the book (7th ed.). Publisher. The title is italic, the edition goes in parentheses after the title, and the publisher’s location is left out. For a chapter in an edited book, add In A. A. Editor & B. B. Editor (Eds.), Title of the book (pp. #–#). Publisher. after the chapter title; editor names are not inverted.

Examples

All sources below are invented for illustration. They are examples of the pattern, not real publications or people.

Journal article

Smith, J., & Lee, K. (2023). Effects of sample size on bias. Journal of Example Studies, 12(3), 45–60. https://doi.org/10.0000/example.123

Book

Smith, J., & Lee, K. (2024). Writing for review boards (2nd ed.). Example Press.

Chapter in an edited book

Smith, J. (2021). Sampling basics. In R. Doe & P. Roe (Eds.), Field methods handbook (pp. 11–26). Example Press.

In-text citation version

Each entry above is cited in the text in one of two forms. In the parenthetical form the author and year sit in brackets: (Smith & Lee, 2023). In the narrative form the author is part of the sentence: Smith and Lee (2023) found that small samples inflate bias. A direct quotation also needs the page: (Smith & Lee, 2023, p. 47).

• Quotations under 40 words go in double quotation marks. Quotations of 40 words or more are set as a block: double-spaced, indented 0.5 in. from the left margin, with no quotation marks.
• With three or more authors, give the first author followed by “et al.” in every in-text citation, including the first. See et al. in references.
• Paraphrase more than you quote. Citing a paraphrase is covered in APA paraphrase citation, and citing a source you only read through another is covered in how to cite a secondary source in APA.

Common errors

APA’s in-text citation checklist is, in effect, a list of what makes a citation incorrect. The mistakes it targets:

• Mismatched spelling or year. The author names and publication years in the text must match the reference list.
• Orphan entries. Every work in the reference list must be cited in the text; either cite it or remove the entry.
• Ambiguous citations. Each in-text citation should match only one reference list entry.
• A direct quote without a page number. Quotations carry the page, as in (Smith & Lee, 2023, p. 47).
• Patchwriting. Swapping a few words or synonyms in a sentence is not a paraphrase, even when the source is cited. See the dictionary entry for plagiarism.
• Overcitation. When you introduce a long paraphrase, one citation is enough. Do not repeat it unless the topic, the source or the paragraph changes.
• Wrong shortening. Three or more authors should be shortened to the first author plus et al. in the text.

For a thesis or manuscript, run the two-way check before submission: pick each citation in the text and find its entry, then pick each entry and find its citation.

Style-guide edition

As of October 2026 the current editions are APA 7th (2020), MLA 9th (2021) and Chicago 18th (2024). APA’s reference guide handout was last updated on 23 March 2026. Chicago 17th is not the current edition.

• APA: author-date, as shown above.
• MLA: the in-text citation is the shortest information that leads to the works-cited entry, usually the author, with a page where there is one: (Baron 194). No “p.” precedes the number. If a work has no page or similar marker, give the author alone. For two authors, join both names with “and”. MLA treats the larger whole that holds a source, such as an anthology holding a story, as its container. See MLA 9 formatting.
• Chicago 18th: a bibliography entry lists up to six authors, and with more than six gives the first three followed by et al. The place of publication is no longer required for books.

Whichever style your journal, department or funder names takes priority. Pick one and apply it throughout.

FAQ

How do I cite sources properly?

Put a short citation in the text wherever you use another person’s words or ideas, and list the full entry in the reference list. Use the template for your style, name every element in the right order, and check that the text and the list agree.

How do I cite sources correctly?

Correct citation means the details match the style guide and match each other: spelling, year, page for quotations, DOI format, and no uncited entries in the list. Run the two-way check described under common errors before you submit. A fuller treatment of quoting is in quoting and citing sources correctly.

Do I need a DOI?

In APA, include a DOI for every work that has one, written as a https://doi.org/ link without a final period.

Sources

Checked 28-29 October 2026.

• APA Style, Reference Guide for Journal Articles, Books, and Edited Book Chapters (7th ed.), last updated 23 March 2026: https://apastyle.apa.org/instructional-aids/reference-guide.pdf
• APA Style, In-Text Citation Checklist (7th ed.): https://apastyle.apa.org/instructional-aids/in-text-citation-checklist.pdf
• MLA Style Center, “In-Text Citations: An Overview”: https://style.mla.org/in-text-citations-overview/
• The Chicago Manual of Style Online, “What’s New in the 18th Edition”: https://www.chicagomanualofstyle.org/help-tools/what-s-new.html