Hernández-Barón, G. M., Juárez, D. I. T., & Steinmann, V. W. (2023). Polystemma stevensii (Apocynaceae, Asclepiadoideae), a new species from Michoacán, Mexico. Phytotaxa, 613(2), 194–200. https://doi.org/10.11646/phytotaxa.613.2.9