Smith, G. F.; Crouch, N. R. A Review of the Nomenclature and Identity of Cotyledon mucronata and C. undulata (Crassulaceae Subfam. Cotyledonoideae), Two Names Variously Applied to Undulate Leaf-Margined Material Generally Included in the Synonymy of Different Varieties of C. orbiculata, With C. mucronata Reinstated at the Rank of Species. Phytotaxa 2025, 714, 40-56.