Answered By: Adolfo Prieto
Last Updated: Jul 11, 2017     Views: 210

The DOI, or digital object identifier, is a unique number assigned to an article.  Not all articles, especially older articles, will have a DOI assigned to them.  If you do see that an article you are citing has a DOI, APA citation style recommends that it be included in the citation.

Please find below a link to more information on the DOI.  Among other things, it explains where the DOI may be found if it has been assigned to an article.  One place to check is the first page of the article itself (usually with the letter DOI or doi in front of the number):

http://www.apastyle.org/learn/faqs/what-is-doi.aspx