How to Cite References in ACS Format
ACS references use a numbered system in many publications. A superscript number in the text points to a full citation in a numbered reference list. The first source cited gets the first number, and later citations of that source use the same number. Check the journal’s author guidelines, since ACS publications may use different citation variants.
The ACS Style Quick Guide and The ACS Guide to Scholarly Communication provide detailed guidance. In general, number sources by order of first appearance, format each entry for its source type, and check that the in-text numbers match the reference list.
How ACS in-text citations work
In the numbered system, place a superscript number near the statement supported by the source. In most cases, it follows the punctuation. Follow the publication’s instructions if they specify different placement.
For example, the first time you cite a source, use ¹. Use ¹ again when citing it later. Give each new source the next number. Arrange the reference list by first appearance, not alphabetically.
When several sources support a statement, group their numbers according to the journal’s preferred format. ACS guidance may allow forms such as ¹,² or ¹⁻³. Use the same format throughout the document.
ACS also uses other citation variants, including italic numbers in parentheses and author–date citations. The required variant depends on the publication. Do not mix variants in one manuscript. Check the journal’s instructions before formatting citations.
Journal article reference format
A journal article entry generally includes the authors, article title, abbreviated journal name, year, volume, page range or article number, and DOI when available. The order and typography depend on the applicable ACS guidance and journal instructions. A general sequence is:
Author(s). Article Title. Journal Abbreviation; year; volume; page range or article number. DOI.
Check names, title, publication details, and DOI against the source itself. Do not guess missing information. Journal abbreviations should follow the standard form. The CAS Source Index (CASSI) Search Tool can help verify them.
ACS references commonly list author surnames followed by initials, with semicolons between names. For long author lists and other cases that do not fit a simple entry, follow the ACS Guide or the target journal’s instructions.
One journal article example
Use a placeholder to see how a journal article entry is organized:
Author, A. A.; Author, B. B. Article Title. Journal Abbreviation; year; volume; page range or article number. DOI: [DOI].
The example shows common reference elements, not a verified publication record. Confirm the journal abbreviation and publication details against reliable source records before using an entry.
Books, websites, and other sources
ACS reference formats vary by source type. A book citation may include the author, italicized title, publisher, place of publication, year, and cited pages. A chapter in an edited book identifies the chapter and may include the editors, book title, publisher, place of publication, year, and page range. Check the applicable guidance for the required elements and their order.
Website references may include an author or organization, page title, site name, URL, and access date. Web content can change, so follow the relevant ACS guidance or journal instructions for the source and required details.
Theses, patents, datasets, and preprints follow their own conventions. Use the format for the source type, not the journal-article template. Check the ACS Style Quick Guide or the publication’s instructions.
Check the citations before submitting
Check that every in-text number points to the correct reference and that every listed source is cited. Confirm that the list follows the order of first appearance, repeated sources keep their original numbers, and bibliographic details match the source. Verify journal abbreviations with CASSI, and include a DOI when one is available and required by the chosen format.
Cite sources you consulted and acknowledge work that informed your writing. The ACS Publications ethical guidelines describe ACS expectations for credit and publication ethics.
Key Takeaways
- In ACS numbered style, in-text numbers correspond to a reference list ordered by first citation.
- Reuse a source’s original number when citing it again.
- Format references by source type and follow the journal’s instructions for the citation variant and reference details.
- Verify author names, publication details, journal abbreviations, and DOIs instead of guessing.
- Cite sources accurately and give credit for work you used.
