Ritzenthaler, Robert E.; Peterson, Frederick A. (December 1954). “Courtship Whistling of the Mexican Kickapoo Indians”. American Anthropologist (American Anthropological Association) 56 (6): 1088–1089. doi:10.1525/aa.1954.56.6.02a00110. JSTOR664763.
Mikko Benjamin Salminen (2016年10月31日). “Phonology”. A grammar of Umbeyajts as spoken by the Ikojts people of San Dionisio del Mar (PhD thesis). 2012年10月6日閲覧。
jstor.org
Ritzenthaler, Robert E.; Peterson, Frederick A. (December 1954). “Courtship Whistling of the Mexican Kickapoo Indians”. American Anthropologist (American Anthropological Association) 56 (6): 1088–1089. doi:10.1525/aa.1954.56.6.02a00110. JSTOR664763.