Rydberg, P. A. (1954). Flora of the Rocky mountains and adjacent plains: Colorado, Utah, Wyoming, Idaho, Montana, Saskatchewan, Alberta, and neighboring parts of Nebraska, South Dakota, North Dakota, and British Columbia (2d ed.). Hafner.
Chicago Style (17th ed.) CitationRydberg, Per Axel. Flora of the Rocky Mountains and Adjacent Plains: Colorado, Utah, Wyoming, Idaho, Montana, Saskatchewan, Alberta, and Neighboring Parts of Nebraska, South Dakota, North Dakota, and British Columbia. 2d ed. New York: Hafner, 1954.
MLA (9th ed.) CitationRydberg, Per Axel. Flora of the Rocky Mountains and Adjacent Plains: Colorado, Utah, Wyoming, Idaho, Montana, Saskatchewan, Alberta, and Neighboring Parts of Nebraska, South Dakota, North Dakota, and British Columbia. 2d ed. Hafner, 1954.