Bound typescript (cover title: "Rotors; drop-center rotor and other Hays rotor patents") with drawings, patents, and black and white photographs. Compiled March 1945, Box: 7, Folder: 3. Russell Randolph Hays papers, RH MS 564. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/278192 Accessed November 23, 2024.