Moyise, Steve. “The Language of the Old Testament in the Apocalypse.” JSNT, no. 76 (2000): 97-113.
This is an excellent article by Dr. Moyise. Combining the evidence of, among others, R. H. Charles and H. B. Swete, in their commentaries, he argues that John was acquainted not only with the Hebrew OT, but also with Greek OT versions.