Citation guides

How to Cite Sources: APA, MLA and Harvard Explained

A practical guide to the three most widely used citation styles. Learn exactly how to format in-text citations and reference lists in APA 7th edition, MLA 9th edition and Harvard style.

Getting your citations right is one of the most practical skills you can develop as a student or researcher. The three citation styles covered here, APA, MLA and Harvard, together account for the vast majority of academic citation requirements worldwide. Each has a distinct logic, and once you understand that logic the rules stop feeling arbitrary.

This guide covers in-text citations, reference list entries for books, journal articles and websites, and the edge cases students most often get wrong: multiple authors, missing dates and DOI formatting.

APA 7th Edition

APA (American Psychological Association) style is the standard in psychology, education, nursing and most social sciences. The 7th edition, published in 2019, introduced several changes that affect how you list multiple authors and format DOIs.

APA in-text citations

APA uses the author-date format. The author's surname and the year of publication go inside parentheses, separated by a comma. When you quote directly, add a page number preceded by "p." or "pp." for a range.

Note the ampersand (&) inside parentheses, but "and" when the authors' names appear in running text: "Smith and Jones (2021) found that..."

APA book reference

APA uses sentence case for book and article titles: only the first word, proper nouns and the first word after a colon are capitalised. The publisher name is written without "Ltd", "Inc." or similar suffixes.

APA journal article reference

The journal name and volume number are italicised; the issue number in parentheses is not. Include the DOI as a hyperlink starting with https://doi.org/ whenever one is available. If there is no DOI and the article was retrieved online, include the URL.

APA website reference

For websites without a date use (n.d.) and add the access date before the URL: "Retrieved March 15, 2024, from https://..." You do not normally need a retrieval date for dated sources.

APA: more than 20 authors

In the reference list, list the first 19 authors, insert an ellipsis (...) and then the final author's name. In-text you always write the first author plus "et al." regardless of how many there are.

MLA 9th Edition

MLA (Modern Language Association) style is used in humanities subjects: literature, languages, film, philosophy and related fields. The 9th edition, released in 2021, introduced the concept of the "core elements" framework, making it easier to cite any source type by applying the same set of fields in the same order.

MLA in-text citations

MLA uses the author-page format rather than author-date. Give the author's surname and the page number with no comma between them. When you name the author in the sentence, you only need the page number in parentheses.

MLA book reference (Works Cited)

MLA uses title case for all book and article titles in the Works Cited list. The publisher and year are separated by a comma, and there is no place of publication. End the entry with a period.

MLA journal article reference

Article titles go in quotation marks; journal names are italicised. Include the volume and issue numbers using "vol." and "no." Note that MLA writes doi:xxxxx rather than the full https://doi.org/xxxxx URL.

MLA website reference

MLA does not require an access date for most websites, but your instructor may ask for one. If the page has no individual author, start with the title in quotation marks (no extra escaping needed here).

MLA: multiple authors

In the Works Cited entry, list up to two authors in full ("Surname, First, and First Surname"). For three or more authors, write only the first author followed by "et al." In-text, any source with three or more authors uses "et al." every time.

Harvard Style (Author-Date)

Harvard is not controlled by a single organisation; it is a family of author-date referencing styles widely adopted at British, Australian and Scandinavian universities. The rules below reflect the standard taught at most UK universities and at Umeå University in Sweden, where small variations exist between departments.

Harvard in-text citations

Harvard in-text citations look almost identical to APA: surname, year, and a page number when quoting. The key difference is that Harvard typically uses a colon before the page number rather than "p.".

Harvard book reference

Unlike APA, Harvard includes the place of publication. The year follows the author name without brackets around it in many university variants (check your institution's style guide for this detail).

Harvard journal article reference

Article titles in Harvard go inside single quotation marks. Commas separate the main elements. The journal name and volume are italicised.

Harvard website reference

Harvard requires an access date for all websites. This is a firm rule that distinguishes it from APA and MLA, both of which make access dates optional. The access date goes at the end in parentheses, introduced by "Accessed:".

Side-by-side comparison

Difficult cases, answered

A source with no author

Move the title into the author position; do not write "Anonymous" unless the work is genuinely credited that way. If an organisation published the page, that organisation is the author.

A source with no date

APA and Harvard mark the missing year explicitly. MLA simply leaves the date out and leans on the access date in the Works Cited entry instead.

A source quoted inside another source

If you cannot read the original, cite the work you actually read. Only that work goes in your reference list, never the one you did not see.

The same author published twice in one year

APA and Harvard append letters to the year, assigned by the alphabetical order of the titles, and the same letters appear in the reference list. MLA distinguishes the works by a shortened title instead.

How many authors before "et al."

This is the single most common point of confusion, because the three styles genuinely differ, and Harvard variants differ from each other too. Check your department's guide if you use Harvard.

Note the asymmetry that catches people out: in APA you write et al. in the text from three authors, but the reference list still names every author up to twenty.

Common mistakes to avoid

Mixing styles. Every source in one document must follow the same citation style. It sounds obvious, but switching between APA and Harvard mid-paper is one of the most common errors markers see.

Forgetting the DOI. If a journal article has a DOI, you must include it in APA and Harvard. Leaving it out is treated as an incomplete reference.

Wrong case for titles.APA and Harvard use sentence case for titles; MLA uses title case. Writing "How To Cite Sources" in an APA reference list is wrong; it should be "How to cite sources".

Missing access dates in Harvard. A URL in a Harvard reference without an access date is incomplete. APA and MLA give you more flexibility here, but Harvard does not.

et al. in the reference list. APA lists all authors up to 20 in the reference list even though you use et al. in-text from three authors onwards. The reference list entry must be complete.