1997 IUCN red list of threatened plants (1997)

Annals of the Missouri Botanical Garden - Missouri Botanical Garden. (Missouri Botanical Garden Press, 2000)

Contributions from the University of Michigan Herbarium - University of Michigan. University Herbarium. (University Herbarium, University of Michigan, 1999)

Contributions from the University of Michigan Herbarium - University of Michigan. University Herbarium. (University Herbarium, University of Michigan, 1999)

Fieldiana Botany - Field Museum of Natural History. (Chicago Natural History Museum, 1986)

Fieldiana Botany - Field Museum of Natural History. (Chicago Natural History Museum, 1986)

Proceedings of the California Academy of Sciences, 4th series - California Academy of Sciences (California Academy of Sciences, 1993)

Proceedings of the California Academy of Sciences, 4th series - California Academy of Sciences (California Academy of Sciences, 1998)