1997 IUCN red list of threatened plants (1997)

Annals of the Missouri Botanical Garden - Missouri Botanical Garden. (Missouri Botanical Garden Press, 1938)

An illustrated flora of the Pacific States: Washington, Oregon, and California - Abrams, Le Roy, 1874 -1956 (Stanford University Press, 1951)

An illustrated flora of the Pacific States: Washington, Oregon, and California - Abrams, Le Roy, 1874 -1956 (Stanford University Press, 1951)

An illustrated flora of the Pacific States: Washington, Oregon, and California - Abrams, Le Roy, 1874 -1956 (Stanford University Press, 1951)

North American flora - New York Botanical Garden (New York Botanical Garden, 1944)