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Notes on the nomenclature and taxonomy of Chiastophyllum and Umbilicus oppositifolius (≡Cotyledon oppositifolia, ≡Chiastophyllum oppositifolium) (Crassulaceae subfam. Sempervivoideae)

. Phytotaxa, 564(2), 239–247. https://doi.org/10.11646/phytotaxa.564.2.7