http://blog.apastyle.org/apastyle/paraphrasing/

All APA Style in-text citations have two parts: the author and the date. Some in-text citations also include page numbers (or other location information when page numbers are not available, as with some online materials). This post describes when and how to include page numbers in APA Style for different kinds of citations as well as how to include the appropriate location information in lieu of page numbers when page numbers are not available.