A Progress Course of Inventive Drawing, by Hermann Krusi and W.J. Whitaker, (photocopy), 1850, Box: 4, Folder: 12. Personal Papers of Marguerite Baumgartel, PP 483. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/133758 Accessed January 13, 2025.