Undercover Detective. Holyoke, Mass.: Double Action Magazines, Inc., December 1938

Undercover Detective. Holyoke, Mass.: Double Action Magazines, Inc., December 1938, Volume: Gilbert D1125. Robert L. Gilbert First Issues collection, Gilbert. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/527903 Accessed December 27, 2025.