Vázquez-Benítez B., Arias S., Cervantes-Sandoval A., Variación morfológica de Coryphantha (Cactaceae): un enfoque multivariado, Acta Botanica Mexicana, 2016, 116:21-47, doi: 10.21829/abm116.2016.1117
A comparison of morphology in 48 taxa historically treated in Coryphantha. It combines measurements of field and herbarium plants with multivariate analyses, identifying useful tubercle, spine and reproductive organ traits. It discusses variation associated with development and habitat, and the boundaries of species complexes.