For Neptunia
Isely, D. 1973. Leguminosae of the United States. I. Subfamily Mimosoideae. Memoirs N.Y. Bot. Gard. 25: 1-152.
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.
Turner, B.L. 1951. Revision of the United States species of Neptunia (Leguminosae). Amer. Midl. Nat. 46: 82-92.
Windler, D.R. 1966. A revision of the genus Neptunia (Leguminosae). Australian J. Bot. 14: 379-420.