Davis AP, Bridson DM (2004) A taxonomic revision of the genus Amaracarpus (Rubiaceae, Psychotrieae). Blumea - Biodiversity, Evolution And Biogeography of Plants 49(1): 25-68. doi: 10.3767/000651904x486188.
There is no corrections for Amaracarpus grandifolius var. humilis yet.