Actually, if you're basing your reference only upon the electronic version of the article, then you should cite as a normal journal reference but add [Electronic version] after the article title name (according to "71. Internet articles based on a print source"). I wouldn't use in press unless you have the hardcopy manuscript in hand from the author(s). And, then, you may, of course, change the reference once it is in print.
Example:
LastName, F., & LastName2, F. (2008). Article title name here [Electronic version]. Journal Title, 7, 101-121.