For Rhynchosia
Grear, J.W. 1978. A revision of the New World species of Rhynchosia (Leguminosae-Faboideae). Mem. New York Bot. Gard. 31: 1-168.
Isely, D. 1998. Native and naturalized Leguminosae (Fabaceae) of the United States (exclusive of Alaska and Hawaii). Monte L. Bean Life Science Museum, Brigham Young Univ., Provo, UT.
Woods, M., and J. Key. 2009. The genus Rhynchosia (Fabaceae) in Alabama. Phytologia 91: 3-17.