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 - Rydberg, Per Axel, 1860 -1931 (The author, 1922)

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 - Rydberg, Per Axel, 1860 -1931 (Rydberg, 1917)

Flora of the Rocky Mountains and adjacent plains, Colorado, Utah, Wyoming, Idaho, Montana, Saskatchewan, Alberta, and neighboring parts of Nebraska, South Dakota, and British Columbia - Rydberg, Per Axel, 1860 -1931 (The author, 1917)

Flora of the Rocky Mountains and adjacent plains, Colorado, Utah, Wyoming, Idaho, Montana, Saskatchewan, Alberta, and the neighboring parts of Nebraska, South Dakota, and British Columbia - Rydberg, Per Axel, 1860 -1931 (The author, 1922)