List of sources:
Du Plessis, E.P. Botanical exploration in South Africa. In Cape Flora: Some of the lectures given on this theme at the University of Cape Town's Public Summer School, January-February 1972. University of Cape Town, Board of Extra-Mural Studies, 1972.
Gunn, M. & Codd, L.E. Botanical exploration of southern Africa. Cape Town: Balkema, 1981.