List of sources:
Dictionary of South African biography, Vol. 2, 1972.
Hall, A.L. A bibliography of South African geology to the end of 1920. Pretoria: Geological Survey, Memoir No. 18, 1922.
Mendelssohn, S. South African bibliography. London, 1910.
Rochlin, S.A. Henry Hall: Pioneer South African cartographer and litterateur. Africana Notes and News, 1961, Vol. 14, pp. 251-265.
Tabler, E.C. The life of Frederick Green. Africana Notes and News, 1953-1955, Vol. 11, pp. 35-42.
Tabler, E.C. Pioneers of South West Africa and Ngamiland, 1738-1880. Cape Town: Balkema, 1973.
Wilmsen, E.N. The Okavango River: Charles John Andersson's search for a water route to the Atlantic. Namibia Scientific Society Journal, 2005, Vol. 53, pp. 79-102.