List of sources:
Cape of Good Hope. Report of the Surveyor-General, 1883-1892, 1895.
Gill, D. On the origin and progress of geodetic survey in South Africa, and the African arc of meridian. Addresses and papers read at the joint meeting of the British and South African Associations for the Advancement of Science held in South Africa, 1905, Vol. 1, pp. 1-25. Johannesburg: South African Association for the Advancement of Science, 1906.
Liebenberg, E.C. Die topografiese kartering van Suid-Afrika, 1879-1972; 'n histories-geografiese ontleding. MA-verhandeling in Geografie, Universiteit van Suid-Afrika, 1973.
National Automated Archival Information Retrieval System (NAAIRS). http://www.national.archives.gov.za/naairs.htm Documents relating to Lieut. Laffan.
National Union Catalogue, pre-1956 imprints. London: Mansell, 1968-1980.
Phillips, W.W. Johannes Jacobus Bosman, a memoir. South African Survey Journal, 1924, Vol. 1(3), pp. 126-136.
Reitz, O.G. August Hammar, 1856-1931. South African Survey Journal, 1968, Vol. 11(4), pp. 31-38; 11(5), pp. 36-43.
Simpson, K. A history of the South African trigonometrical system. South African Journal of Surveying and Mapping, 1989, Vol. 20(3), pp. 109-119.
South African bibliography to the year 1925. London: Mansell, 1979.
Watermeyer, G.A. Surveying and geodesy. South African Geographical Journal, 1929, Vol. 12, pp. 5-13.
Who was who, Vol. 3, 2nd ed. London: Adam & Black, 1967.
Zakiewicz, T. The African arc of the 30th meridian. South African Journal of Surveying and mapping, 1997, Vol. 24(2), pp. 65-82.