Lantz (Robyns) 2005 - Lantz H, Bremer B (2005) Phylogeny of the complex Vanguerieae (Rubiaceae) genera Fadogia, Rytigynia, and Vangueria with close relatives and a new circumscription of Vangueria. Plant Systematics and Evolution 253(1-4): 159-183. doi: 10.1007/s00606-005-0313-9.
There is no corrections for Vangueria cinerascens var. richardsiae yet.