APA Style - 6th edition 

DOI = Digital Object Identifier

• 2010 Publication Manual (6th edition): Use a DOIs (if assigned to the article) in citing articles whether accessed in the print or electronic form.
• 2007 Publication Manual Update: Use a DOI (if assigned to the article) in citing articles accessed in electronic format.
• 2001 Publication Manual (5th edition): DOIs did not exist in 2001.

A Digital Object Identifier (DOI) is prefereable to a Uniform Resource Locator (URL) when citing an online resource.

A DOI is a digital object identifier – a unique alphanumeric code that gives a persistent link to the web location for an electronic item. At this point, more and more journal articles are assigned DOIs.  DOIs are commonly seen on current electronic journal articles, but are often also included in the print version of the article.  Here is an example of a DOI:

 10.1111/j.1471-8847.2007.00193.x 

How do I find the DOI for an article?

1) First, the first page of the article may have a DOI.  A DOI is identified as such on the first page; i.e.,

 DOI: 10.1016/j.anireprosci.2006.12.005   

2) DOIs are often included in database records.  Thus, if you are searching a library database like Academic Search Premier or CINAHL, if a DOI is assigned to an article, you will find in the database record for that article.

3) DOIs may also be found in the bibliography of an article – as authors are now using DOIs as a citation tool.  If you find a DOI in a bibliography and want to find the actual article (or at least further citation information), you need to use a DOI resolver (see http://dx.doi.org/).