References

For Astrophytum

M.D. Vargas-Luna, P. Hernández-Ledesma, L.C. Majure, R. Puente-Martínez, H.M. Hernández Macías, R.T. Bárcenas Luna. 2018. Splitting Echinocactus: morphological and molecular evidence support the recognition of Homalocephala as a distinct genus in the Cacteae. PhytoKeys 111: 31-59. Google Scholar

Zimmerman, A.D., and B.D. Parfitt. 2003h. Astrophytum. In Flora of North America Editorial Committee. 2003b. Flora of North America north of Mexico. Volume 4, Magnoliophyta: Caryophyllidae, part 1. Oxford Univ. Press, New York, NY. 559 pp. Google Scholar