APS Citation Style: A Complete Formatting Guide

APS citation style is the numbered, bracket-based referencing system the American Physical Society requires for its Physical Review journals, and it is built on a modified version of the Chicago Manual of Style rather than an author-date format like APA. Instead of alphabetizing sources, APS style numbers each reference in the order it first appears in the text, then reuses that number every time the source is cited again. This guide walks through the in-text bracket rules, how to format a reference list for the source types students and researchers cite most, and where APS style diverges from APA, MLA, and standard Chicago.

What Is APS Citation Style?

APS style is the citation format published by the American Physical Society for authors submitting to its Physical Review journals, including Physical Review Letters and the Physical Review A through E series. Coastal Carolina University’s physics research guide describes it plainly: APS style is a modified version of the Chicago Manual of Style, adapted for the fast-moving pace of physics publishing, where a paper might cite dozens of sources and readers need to scan a reference list quickly rather than parse author names mid-sentence.

You will mostly encounter APS style in undergraduate and graduate physics or astronomy coursework, lab reports, and manuscripts prepared for submission to an APS journal. The American Physical Society’s own Style Basics page sets out the manuscript-level formatting rules that this citation system fits into. If your course or department uses a different discipline’s rules instead, our citation style hub covers the other formats you’re most likely to need.

In-Text Citations in APS Style

APS style cites sources with a number in square brackets, placed right after the claim or quotation it supports, for example: superconductivity was first explained by pairing electrons into bound states [1]. The number is not the page number and it is not tied to the alphabet. It simply reflects the order in which that source first shows up in your paper.

• First citation
• Repeat citation
• Multiple sources
• Range of sources

Citing Multiple or Repeated Sources

The first time you cite a source, it gets the next unused number, such as [1]. If you cite that same source again later in the paper, you reuse [1], you never assign it a new number. When a single sentence draws on more than one source, separate the numbers with a comma, like [2,3]. When you are citing a consecutive run of three or more sources, use a hyphen to show the range, like [4-6]. Some journals also allow the citation number to sit as a superscript rather than in brackets, so always check your specific journal’s or instructor’s formatting sheet before submitting.

Formatting an APS Reference List

The reference list at the end of an APS-style paper is numbered to match the in-text citations, in the order those citations first appear, not alphabetically by author surname. Authors are listed with initials before the surname (for example, J. D. Jackson, not Jackson, J.D.), and the format varies slightly by source type.

Reference List Templates by Source Type

The table below covers the five source types writers cite most often in APS citation style, with the APS template and a real worked example for each.

Source type	Template and example
Journal article	Author initials and surname, abbreviated journal title, volume, page or article number (year). J. Bardeen, L. N. Cooper, and J. R. Schrieffer, Phys. Rev. 108, 1175 (1957).
Book	Author initials and surname, Title, edition (Publisher, City, year). J. D. Jackson, Classical Electrodynamics, 3rd ed. (Wiley, New York, 1999).
Website	Organization or author, Page title, URL (year accessed). National Institute of Standards and Technology, NIST Reference on Constants, Units, and Uncertainty, https://physics.nist.gov/cuu/ (2024).
Conference proceedings	Author initials and surname, in Proceedings title, edited by Editor Name (Publisher, City, year), p. page. S. Weinberg, in Proceedings of the XXIII International Conference on High Energy Physics, edited by S. Loken (World Scientific, Singapore, 1987), p. 3.
Preprint (arXiv)	Author initials and surname, Title, arXiv identifier. E. Witten, Anti-de Sitter Space and Holography, arXiv:hep-th/9802150.

Citing a website in APS style works the same way as any other entry: number it by first appearance, not alphabetically. For the general rules on pulling a citation from a webpage rather than a journal, see our guide to citing a website in an essay. For the exact formatting rules APS applies to its own Physical Review journals, see the Society’s References in Physical Review Journals page and the full APS Journals Style Guide PDF, which includes worked examples starting on page 7.

APS Style vs. Other Citation Styles

The biggest practical difference between APS style and APA or MLA is that APS never puts an author’s name or a publication year directly in your sentence. APA and MLA rely on parenthetical author-date or author-page citations that a reader can recognize without flipping to the reference list. APS trades that readability for compactness, which matters in a field where a single paper can cite over a hundred sources.

That second example is standard APA in-text formatting, not APS, because it names the authors and the year inline instead of using a bracketed number. Chicago’s own author-date variant looks similar to that incorrect example too, which is why it’s worth double-checking which citation style your assignment actually calls for. If your assignment calls for APA, MLA, or Chicago author-date instead of APS, see our guides on how to cite journal articles, how to cite books, or generate a citation directly with the Chicago author-date generator.

Common APS Citation Mistakes to Avoid

Most APS citation style errors come from applying habits learned in APA or Chicago author-date classes, where the rules genuinely are different. The table below lists the mistakes that show up most often in student papers and lab reports, and the fix for each.

Mistake	Fix
Alphabetizing the reference list	Order it by first in-text citation appearance instead. The first source cited in your paper is reference [1], regardless of the author’s surname.
Naming the author inline, mid-sentence	Use a bracketed number after the claim, such as [1], instead of an author-date parenthetical.
Assigning a new number to a repeat citation	Reuse the number that source was already given the first time you cited it.
Writing out the full journal name	Use the standard abbreviated title in the reference list, such as Phys. Rev. Lett. for Physical Review Letters.

Frequently Asked Questions