Hensold (Silv) 1988 - Hensold N (1988) Morphology and Systematics of Paepalanthus Subgenus Xeractis (Eriocaulaceae). Systematic Botany Monographs 23: 1-150. doi: 10.2307/25027709.
There is no corrections for Paepalanthus superbus var. niveoniger yet.