Puff (Verdc.) 1981 - Puff C (1981) Studies in Otiophora Zucc. (Rubiaceae). 1. The Tropical African and Madagascan taxa. Bulletin Du Jardin Botanique National De Belgique 51: 119-141. doi: 10.2307/3667737.
There is no corrections for Otiophora villicaulis var. iringensis yet.