Laumer - Retief's Ransom (1969), The Undefeated (1969), Retief (1970-[19]71), The Planet Breakers (1971), Box: 12, Folder: 14. Corporate Papers of the Robert Mills Literary Agency, MS 307. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/230350 Accessed November 23, 2024.