Wickens & M.Bywater (Fisch. & Mey.) 1980 - Wickens GE, Bywater M (1980) Seed Studies in Crassula Subgen. Disporocarpa: Studies in the Crassulaceae for the 'Flora of Tropical East Africa': I. Kew Bulletin 34(4): 629-637. doi: 10.2307/4119060.
There is no corrections for Crassula alata subsp. pharnaceoides yet.