Although science fiction (sf) had been published before the 1920s, it did not begin to coalesce into a separately marketed genre until the appearance in 1926 of "Amazing Stories", a pulp magazine published by Hugo Gernsback. By the end of the 1930s the field was undergoing its first boom. Gernsback lost control of "Amazing Stories" in 1929; it was sold to Teck Publications, and then in 1938 it was acquired by Ziff-Davis. The following year Ziff-Davis launched "Fantastic Adventures" as a companion to "Amazing"; the first issue was dated May 1939, and the editor of "Amazing", Ray Palmer, took on responsibility for the new magazine as well.