Typescript (in looseleaf binder labeled "Open/Close Timing, 1967, 32 ratio, Even-Even Ports") with drawings and color photograph (cone resonator testing), Box: 8, Folder: 25. Russell Randolph Hays papers, RH MS 564. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/278233 Accessed May 08, 2024.