1997 IUCN red list of threatened plants (1997)

Contributions from the University of Michigan Herbarium - University of Michigan. University Herbarium. (University Herbarium, University of Michigan, 2005)

Fieldiana Botany - Field Museum of Natural History. (Chicago Natural History Museum, 1974)

Proceedings of the California Academy of Sciences, 4th series - California Academy of Sciences (California Academy of Sciences, 2010)

Proceedings of the California Academy of Sciences, 4th series - California Academy of Sciences (California Academy of Sciences, 2010)

Proceedings of the California Academy of Sciences, 4th series - California Academy of Sciences (California Academy of Sciences, 2010)

Proceedings of the California Academy of Sciences, 4th series - California Academy of Sciences (California Academy of Sciences, 2010)

Publication. Field Museum of Natural History Botanical series - Field Museum of Natural History. (Field Museum of Natural History, 1947)

Publication. Field Museum of Natural History Botanical series - Field Museum of Natural History. (Field Museum of Natural History, 1947)