Strickler, D. (1997). Northwest penstemons: 80 species of Penstemon native to the Pacific Northwest. Flower Press.
Style de citation Chicago (17e éd.)Strickler, Dee. Northwest Penstemons: 80 Species of Penstemon Native to the Pacific Northwest. Columbia Falls, Mont.: Flower Press, 1997.
Style de citation MLA (8e éd.)Strickler, Dee. Northwest Penstemons: 80 Species of Penstemon Native to the Pacific Northwest. Flower Press, 1997.
Attention : ces citations peuvent ne pas être correctes à 100%.