How do I find the DOI for an article?
DOI (Digital Object Identifier) is a unique number used to identify online publications.
Some bibliography styles such as APA require the inclusion of the DOI when one is available. Not all articles have a DOI.
You can find the DOI by entering an article's reference information in the CrossRef's search form.
Here is a link to the APA Style Blog that has information about finding the DOI.