Hilliard, O.M. & Burtt, B.L. 1987. The Botany of the Southern Natal Drakensberg. National Botanic Gardens, CTP Book Printers, Cape Town.
http://pza.sanbi.org/references/hilliard-om-burtt-bl-1987-botany-southern-natal-drakensberg-national-botanic-gardens-ctp