J. Weedin

Chromosome numbers in the Compositae, XII: Heliantheae

R. M. King, A. Powell, H. Robinson, 1981 .

Cacti of the Trans-Pecos and Adjacent Areas

J. Weedin, A. M. Powell, 2004 .

Chromosome numbers in Chihuahuan Desert Cactaceae. III. Trans-Pecos Texas.

J. Weedin, A. Michael Powell, A. M. Powell, 1978, American journal of botany.

Chromosome Numbers in Compositae, XV: Liabeae

R. M. King, A. Powell, H. Robinson, 1985 .