APA uses a Digital Object Identifier (DOI), when it is available. A DOI is unique to each document and is considered more stable than a URL, which might change.
A DOI is usually found on the first page of the article or is listed on the database record. If there is no DOI, use the URL of the journal's website, even if you found the article in a database. (You may have to search for the website on the Internet.)
If you are using an article that you found in the hard copy of the journal (which means you are holding the complete journal in your hand), leave off all information about the retrieval.
Book review in print academic journal
Shoaf, E.C. (2011). On leading and being led. [Review of the book Leading from the middle, by John Lubans.] College and Research Libraries News, 72(2), 102-103.
Article in print academic journal
Meyerowitz, J. (2009). Transnational sex and U.S. history. The American Historical Review, 114, 1273-1286.