License agreement with Helicopter Corporation of America, September 13, 1950, granting license rights to U.S. patent for helicopter filed June 29, 1946 by George de Bothezat; monograph: De Bothezat Aeronautical Corporation; its purpose and scope, by John H. Sears. (1926), Box: 7, Folder: 19. Russell Randolph Hays papers, RH MS 564. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/278208 Accessed November 23, 2024.