Memoirs of The New York Botanical Garden
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of Vascular Plants of Northeastern United States and adjacent Canada
Details: Lotus rigidus (Benth.) Greene x L. wrightii (A.Gray) Greene
Isely, Duane. 1981. Leguminosae of the United States. III. Subfamily Papilionoideae: tribes Sophoreae, Podalyrieae, Loteae. Mem. New York Bot. Gard. 25 (3): 1-264.
Lotus rigidus (Benth.) Greene x L. wrightii (A.Gray) Greene
Ottley (1944) believed collections from various parts of Arizona to represent this hybrid combination. Some of her determinations are plausible, but I have referred most of the subject collections to one species or the other.