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Citations & Style Guide

Information and resources on how to cite references correctly.

Citations for Online Sources

APA, 7th edition

  • APA Style DOIs and URLs addresses when to include digital object identifiers (DOIs) and uniform resource locators (URLs) in citations for online articles.
  • APA Style Database Information in References provides guidelines on when to include database information in online article citations, which is covered in Section 9.30 of the APA Publication Manual, 7th edition.

APA, 6th edition

Chicago, 17th edition

  • Chicago Manual of Style: Web Sources Basic guidelines and samples of citations for various online documents in Chicago style from the Purdue Online Writing Lab (OWL).
  • Chicago-Style Citation Quick Guide General guide to citing in both the notes and bibliography style and the author-date style. Includes examples of citations to various types of electronic publications.

MLA, 8th edition

Citing Online Sources

When citing an electronic source, it is better to risk providing too much information rather than too little. Be sure that your reader has enough information to go back to your source if necessary. Although a citation to a publication in electronic format follows basically the same principles as a citation to a paper document, citing an electronic publication or content from a website may present a few peculiar challenges. For instance:

  • A document may only have a file name instead of a title or a login name instead of an author.
  • The content of a website may change frequently without notice.
  • The concept of pagination as it pertains to paper publications is usually absent in electronic documents and website pages.
  • Versioning may require additional information to uniquely identify the source, especially for content that appears in multiple formats, or across multiple sites or platforms, or in multiple iterations as with software and some data sets.

DOIs & Permanent URLs


Most citation styles prefer that you include the DOI (when available) for online sources such as articles. The term DOI is an acronym for Digital Object Identifier and unlike URLs, DOIs are uniquely assigned and will stay with the source even when the site structure or platform of access changes. 

The DOI is a numeric or alphanumeric string of text that may be used as an URL (or search term) to locate an online resource. The DOI may look something like this: doi:10.00/00.00/00000/0000, or this

To locate the DOI, look on the first page of the article. Other common places to locate the DOI may be the footer, the record page, or the publisher's website. If you are having trouble locating a DOI, try checking or

Permanent Links

For online sources without DOIs, it is extremely important to make sure the URL used to point back to the source is not a search string or a proxy link. It is usually best to go to the publisher's home site if you are unsure whether the link you used to access the source is the permanent link for the source.  

Additional Links