The Chadronian, Orellan, and Whitneyan North American Land Mammal AgesColumbia University Press156–168
Prothero, Donald R. and Emry, Robert J. 2004. "The Chadronian, Orellan, and Whitneyan North American Land Mammal Ages." In Late Cretaceous and Cenozoic Mammals of North America: Biostatigraphy and Geochronology. Michael, O. Woodburne, editor. 156–168. Columbia University Press.