Sánchez D., Gómez-Quintero D., Vargas-Ponce O., Carrillo-Reyes P., Dávila-Aranda P., Species delimitation in the Echinocereus pulchellus complex (Cactaceae), Brittonia, 2020, 72(4):433-452, doi: 10.1007/s12228-020-09632-x
A multivariate analysis of morphological characters in populations previously assigned to five subspecies of Echinocereus pulchellus. The authors recognise four species and provide descriptions, an identification key and habitat information, while relating part of the morphological variation to climate.