Ill. Fl. N. U.S., ed. 2 2: 569 (1913)
[An illustrated flora of the northern United States, Canada and the British possessions]
[An illustrated flora of the northern United States, Canada and the British possessions]
510932 759719 Pediocactus simpsonii (Engelm.) Britton & Rose [0]
N.L. Britton, J.N. Rose, Cact., vol. 3 : t. 8 (1922) [M.E. Eaton]
444555759689 Pediocactus knowltonii L.D. Benson
W. Curtis, Bot. Mag., ser. 2, vol. 1(): : p. 183 (1984) [C. Grey-Wilson]
