For Orbexilum
Grimes, J.W. 1988. Systematics of New World Psoraleae (Leguminosae-Faboideae). Ph.D. dissertation, Univ. of Texas at Austin.
Grimes, J.W. 1990. A revision of the New World species of Psoraleeae (Leguminosae: Papilionoideae). Memoirs N.Y. Bot. Gard. 61: 1-114.
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. 2008. Revision of the genus Orbexilum (Fabaceaea: Psoraleeae). Lundellia 11: 1-7.
Vincent, M.A. 2014. Neotypification of Trifolium psoralioides Walter (Fabaceae) and its transfer to Orbexilum. Phytoneuron 2014-36: 1-7. Published 25 March 2014. ISSN 2153 733X