Porembski S., Functional Morphology of Aztekium ritteri (Cactaceae), Botanica Acta, 1996, 109(2):167-171, doi: 10.1111/j.1438-8677.1996.tb00557.x
A microscopic description of the Aztekium ritteri stem, distinguishing exposed and shaded surfaces. The paper presents stomatal distribution, differences in cuticle thickness, calcium oxalate crystals and changes in groove opening during dehydration. It discusses the functional significance of this organisation.