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Benson, Lyman
The Cacti of Arizona. University of New Mexico Press, 1950.
Clements, Frederic E. and Clements, Edith S.
Rocky Mountain Flowers. The H. W. Wilson Co., New York, 1928.
Coulter, John M. and Nelson, Aven
New Manual of Botany of the Central Rocky Mountains. American Book Company, New York, 1919.
Dodge, Natt N. (Drawings by Jeanne R. Janish)
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