Answered By: Kim Read Last Updated: Jun 08, 2016 Views: 40
APA calls this type of article an "advance online publication". Often these articles will already have a doi assigned, but the volume and issue numbers are not assigned. Include the rest of the article information that you normally would for an article reference. Before the doi, include this phrase: Advance online publication.
Here's an example from the APA style blog:
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
Be sure to double space your references (the above example is single spaced)