Pettingill, Olin Sewall. "A Laboratory and Field Manual of Ornithology". Minneapolis: Burgess, 1950, Box: 98, Folder: 34. Sauer's Gouldiana Research about John Gould and other papers, MS 304. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/205391 Accessed November 28, 2024.