"O.K." Comics. St. Louis, Missouri: Hit Publications, Inc., July 1940

"O.K." Comics. St. Louis, Missouri: Hit Publications, Inc., July 1940, Volume: Gilbert D724. Robert L. Gilbert First Issues collection, Gilbert. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/526916 Accessed December 27, 2025.