Seeds of woody plants in the United States. Raunkiaer, C. 1934. The life forms of plants and statistical plant geography. Schultz, Brad W. 1987. Shiflet, Thomas N., ed.
Rangeland cover types of the United States.
Society for Range Management. U.S. Department of Agriculture, Forest Service, Intermountain Research Station. U.S. Department of Agriculture, Forest Service, Intermountain Research Station. Stickney, Peter F. 1989. Seral origin of species originating in northern Rocky Mountain forests.