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ACS - Referencing Guide

ACS Style

About ACS Style

ACS Style uses a notational method of referencing when referring to a source of information within the text of a document.

In its simplest form, a number in superscript format placed in the text of the essay, indicates the relevant reference:

The superscript number appears outside the punctuation if the citation applies to a whole sentence or clause. There is no space between the punctuation and the superscript number.

Citations are numbered consecutively in the order in which they appear in the document, including references cited in the text and in non-text content such as tables and figures.

Once a source has been cited, the same number is used in all subsequent references. No distinction is made between print and electronic references when citing within the text.

Each citation corresponds to a numbered reference containing publication information about the source cited in the reference list at the end of the publication, essay or assignment:

A numbered list of references must be provided at the end of the paper.

The list should be arranged in the order of citation in the text of the publication, assignment or essay, not in alphabetical order.

List only one reference per reference number. Reuse the original number rather than assigning a new number if the same reference is used more than once.

It is very important that you use correct punctuation and that the order of details in the references is correct.

See Reference List Entries or All Examples for details on how to construct references for specific resources such as books, journals and web pages.

Important Information

Created October 2010; modified June 2019; modified May 2023 using ACS Style Quick Guide

The American Chemical Society (ACS) Style is used primarily for publications in chemistry and allied sciences.

Please remember to check with your unit co-ordinator or tutor before submitting your assignments, as their style preference may vary from the guidelines presented here.

When using EndNote referencing software, please use the following output style - ACS. For information about EndNote, please see the EndNote Guide.


This referencing guide follows the principles and examples given in the ACS Style Guide: Effective Communication of Scientific Information published by the American Chemical Society (ACS), 3rd edition, 2006.

This publication constitutes the authoritative international guide to ACS publication standards and style.