Campbell, Lyle(英语:Lyle Campbell) (1997). American Indian Languages: The Historical Linguistics of Native America. Oxford: Oxford University Press. pp. 286-288
Goddard, Ives(英语:Ives Goddard) (1996). "The Classification of the Native Languages of North America". In Ives Goddard, ed., "Languages". Vol. 17 of William Sturtevant, ed., Handbook of North American Indians. Washington, D.C.: Smithsonian Institution. pg. 318
Trask, R. L.(英语:Larry Trask) (2000). The Dictionary of Historical and Comparative Linguistics. Edinburgh: Edinburgh University Press. pg. 85