The Digest Index
compiled by Kenneth R. Johnson
Published electronically by BookScans.com in .pdf format. 169 pages. This is probably the most complete (and certainly the most accurate) listing of digest-sized vintage paperback books in existence today. Johnson starts with an extremely interesting introduction outlining a brief history and pertinent observations, then he indexes the books first by Publisher, then again by Author and finally by Title. A dozen or so scanned pages are listed in a separate section to highlight footnoted comments.
Click HERE to go to the book.