Publishers have started to assign a Digital Object Identifier (DOI) to journal articles and other types of documents. A DOI is a unique alpha-numeric code given to individual online works. The DOI usually appears at the top of the article or in the database record for the article.
At the moment, not all publishers provide DOIs. Some library databases such as PsycINFO provide a DOI for each article. When a DOI is provided, your should provide it at the end of your APA reference. Items with a DOI no longer need the database name in the citation.
APA suggests that when DOIs are available, you include them for both print and electronic sources.
There is no need to include the retrieval date unless the source information is likely to change.
Some databases do not provide DOIs. If the article you are citing does not include a DOI, provide the home page URL of the journal. If you are accessing the article from a library database, you will need to do a web search to locate the URL. You do not have to include the name of the database in the citation.
If there is no DOI provided, try searching CrossRef.org, a free DOI lookup.