Majure L. C., Judd W. S., Soltis P. S., Soltis D. E., Taxonomic revision of the Opuntia humifusa complex (Opuntieae: Cactaceae) of the eastern United States, Phytotaxa, 2017, 290(1):1-65, doi: 10.11646/phytotaxa.290.1.1
A revision of the Opuntia humifusa complex from the eastern United States. It contains a key, morphological descriptions, typifications, maps, phenology and an extensive specimen list. It distinguishes O. humifusa and O. cespitosa among others, and discusses the polyploid origin of the group.