Flora of the northwest coast, including the area west of the summit of the Cascade Mountains, from the forty-ninth parallel south to the Calapooia Mountains on the south border of Lane County, Oregon - Piper, Charles V. (Charles Vancouver), 1867 -1926 (Press of the New Era Printing Company, 1915)

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, 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, and British Columbia - Rydberg, Per Axel, 1860 -1931 (The author, 1917)