APA (7th ed.) Citation

Ayensu, E. S., & DeFilipps, R. A. (1978). Endangered and threatened plants of the United States. Smithsonian Institution.

Chicago Style (17th ed.) Citation

Ayensu, Edward S., and Robert A. DeFilipps. Endangered and Threatened Plants of the United States. Washington: Smithsonian Institution, 1978.

MLA (9th ed.) Citation

Ayensu, Edward S., and Robert A. DeFilipps. Endangered and Threatened Plants of the United States. Smithsonian Institution, 1978.