Ruder, K. E., Acquisition of Early Verb Forms, Bio-Med KU# 4048-x706-4, April 1, 1980-December 31, 1980, Box: 69, Folder: 26. 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/455658 Accessed May 23, 2025.