Answered By: Mary Ann Naumann
Last Updated: Apr 07, 2015     Views: 7384

The APA Style Blog addresses this problem http://blog.apastyle.org/apastyle/advance-online-publication/

Quoting from the Blog Post:

Advance Online Publication
Now, onward into the brave new world of articles being available before they are available—in specific issues of print or online-only journals, that is. Definitions of advance online publication vary among journal publishers. Sometimes articles appearing in advance online publication databases have been edited, sometimes they have not. They may or may not have a DOI assigned. For many publishers, these articles are the version of record and thus are, technically, published, belying the title of this post.

Yet the question remains: How does one create references for advance online publication articles? Provide the author(s), year of posting, title of the article, name of the journal, the notation Advance online publication, and the DOI or the URL of the journal’s home page.

Muldoon, K., Towse, J., Simms, V., Perra, O., & Menzies, V. (2012). A longitudinal analysis of estimation, 
   counting skills, and mathematical ability across the first school year. Developmental Psychology.
   Advance online publication. doi:10.1037/a0028240

As your article is heading toward submission and publication, keep following up on your references that are moving through their own publication processes, and update them as you are able. If possible, refer to the final versions of your sources.