References
Majure, L.C., W.S. Judd, P.S. Soltis, and D.E. Soltis. 2012a. Cytogeography of the Humifusa clade of Opuntia s.s. Mill. 1754 (Cactaceae, Opuntioideae, Opuntieae): correlations with pleistocene refugia and morphological traits in a polyploid complex. Comparative Cytogenetics 6: 53-77. Google Scholar