List of sources:
Beyers, C.J. Die navorsingswaarde van die oudste kaarte van Kaapstad. South African Archives Journal, 1965, No. 7, pp. 38-44.
Dictionary of South African biography, Vol. 5, 1987.
FamilySearch: Johan Wittebol. https://ancestors.familysearch.org/en/G6ZY-2DV/johan-wittebol-1650-1681
Fisher, R. Land surveyors and land tenure at the Cape, 1657-1812. In C.G.C. Martin & K.J. Friedlaender (eds), History of surveying and land tenure in South Africa: Collected papers (pp. 55-88). University of Cape Town, Department of Surveying, 1984.