As I detail on the Not in Currey page, every serious collector of science fiction uses L. W. Currey’s Science Fiction and Fantasy Authors: A Bibliography of First Printings of Their Fiction, published by G. K. Hall & Co., Boston, 1979 (CURREY) as a major reference book to hunt down first editions and their variants. Most of the serious f&sf bookdealers also make reference to CURREY. The CURREY name is so powerful that it creates a blind spot. Authors not listed in CURREY almost never have variants listed in descriptions of books put on sale. Worse, most listings of those books don’t mention the color of the boards or the number of titles mentioned on the rear cover ad – the two major variants Gnome used – at all. Known variants are hidden out there. We don’t know how many of these exist. More keep getting discovered.
The next most used reference guide for Gnome variants is The Science-Fantasy Publishers: A Critical and Bibliographic History, 3rd edition, by Jack L. Chalker and Mark Owens (Mirage Press, 1991) (CHALKER). CHALKER mentions every book Gnome published. Many variants can be found there for authors not listed in CURREY. I’m putting those in this separate section to call attention to them.