"Kapalka and Vratil/ 50th anniversary/ Hess, Vratil, Enis, Solomon", 1988, Box: 32, Folder: 49-51. Wilbur D. Hess collection, RH MS 1526. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/459587 Accessed June 03, 2024.