[Zimmerman A. D., Parfitt B. D., Lophophora, Flora of North America North of Mexico, Oxford University Press, New York, Oxford, 2003c, tom 4, s. 242]
The floristic treatment includes a description of Lophophora williamsii, data on its body, root and flowers, and its range, habitats and phenology. The online counterpart of the species description was read. The name's authorship retains the treatment used at publication.