Digital Object Identifier (DOI): DOI Citation

In any citation style (APA, MLA, etc.), the DOI is normally listed at the end of the citation.

Examples:

Online/Electronic Articles in Periodicals (journals, magazines, newspapers, newsletters)

Since July 2007, APA has emphasized using the DOI (Digital Object Identifier) when referencing articles. Unlike URLs which may change over time, the DOI is unique to an individual work. Not all publishers participate in the DOI initiative; as a result, an article may or may not have a DOI assigned.
In the 6th edition of the Manual, APA presents a simple approach for referencing online articles:

Article is assigned a DOI
OR
Article is not assigned a DOI

Usually only journals (primarily scholarly/research), and some online books—are assigned a DOI. Magazines, newspapers, newsletters, and most online documents/reports do not have a DOI.  

Use the following sequence to determine how to format your article reference. Tools & examples appear below.

• When an article is assigned a DOI, the APA standard is that researchers (including students) will always locate the DOI, and use the reference format which includes the DOI.
  This is not an “either-or” situation where the researcher may choose to ignore a DOI.

• When there is no DOI assigned, provide the periodical home page web address (URL).

• When an article is not assigned a DOI, is either published in a discontinued periodical or the periodical web web page does not exist, and online content is ONLY available in an electronic database such as CINAHL or JSTOR, provide the entry page URL of the database which holds the article. Although this type of reference is rare for articles, it may occur especially when the journal is discontinued.

Note: It is unacceptable to substitute an assigned DOI with the journal URL or database URL.