Montanucci, Richard R., and Klaus-Peter Kleszewski. “A Taxonomic Evaluation of Astrophytum Myriostigma Var. Nudum (Cactaceae)”. Journal of the Botanical Research Institute of Texas 14, no. 2 (December 7, 2020): 255-264. Accessed September 21, 2021. https://journals.brit.org/jbrit/article/view/1006.