Notes on the nomenclature and taxonomy of Chiastophyllum and Umbilicus oppositifolius (≡Cotyledon oppositifolia, ≡Chiastophyllum oppositifolium) (Crassulaceae subfam. Sempervivoideae)
. Phytotaxa. 564, 2 (Sep. 2022), 239–247. DOI:https://doi.org/10.11646/phytotaxa.564.2.7.