"Pitch Variating Mechanism for Blades of a Rotating Wing System" [notarized Hays statement], December 15, 1934, Box: 6, Folder: 9. Russell Randolph Hays papers, RH MS 564. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/278177 Accessed October 05, 2024.