References
For Echinocereus
Williamson, P.S., P. Berresford, S.D. Fehlberg, M. Terry, A. W. Strong, J. McKinney, and A. Ermakova. 2022. Occurrence and phylogeny of the endangered Texas endemic Echinocereus fitchii subsp. albertii. Bradleya 40:27-48. Google Scholar
Zimmerman, A.D., and B.D. Parfitt. 2003d. Echinocereus. 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