Core Grant, MRRC, KU # 4060, Miscellaneous, Kansas Mental Retardation Research Center, Annual Report of the Research Training Section, Prepared by Earl C. Butterfield, May, 1968, Box: 18B, Folder: 23. University of Kansas Schiefelbusch Institute for Life Span Studies records, RG 35. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/452741 Accessed July 10, 2025.