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According to the book Mastering Scientific and Medical Writing, the preferred way to cite an item that has been accepted for publication is to use the term Forthcoming after the title of the journal. Apparently NLM prefers that term because not all items will be printed.
Our APA citation guide has information about citing articles In Process and In Press: https://guides.lib.unc.edu/APA/other-sources#s-lg-box-27445151.
The APA Style Blog also has resources for citing unpublished works and preprint article references.