S. Prentiss Baldwin and S. Charles Kendeigh.
Scientific Publications of the Cleveland Museum of Natural History, Vol. III: Physiology of the Temperature of Birds; Contribution No. 21 from The Baldwin Bird Research Laboratory, Gates Mills, Ohio. Cleveland: Cleveland Museum of Natural History, 1932. Smithsonian Libraries.
www.biodiversitylibrary.org/item/122946#page/14/mode/1up.