Montanucci, Richard R., and Klaus-Peter Kleszewski. 2021. “Taxonomic History, Comparative Morphology, and Variation in Astrophytum Myriostigma and Its Subspecies Tulense (Cactaceae)”. Journal of the Botanical Research Institute of Texas 15 (2):327-41. https://doi.org/10.17348/jbrit.v15.i2.1152.