List of sources:
Bozzoli, G.R. Forging ahead: South Africa's pioneering engineers. Johannesburg: Witwatersrand University Press, 1997.
Council for Geoscience. Catalogue of Publications of the Geological Survey and Government Publications on the Earth Sciences (comp. R.R.M. Price). Pretoria: Council for Geoscience, 1997.
Dictionary of South African biography, Vol. 4, 1981.
FamilySearch: Robert William Nelson Kotze. https://www.familysearch.org/en/tree/person/details/KH93-2ZG
Geological Society of South Africa. Transactions (and Proceedings), 1897, Vol. 2(1); 1899, Vol. 4(4); 1906, Vol. 10; 1915, Vol. 18; and 1920, Vol. 23: Lists of members.
Hall, A.L. A bibliography of South African geology.... Pretoria: Geological Survey, Memoirs No. 18 (1922), 25 (1927), and 27 (1931).
Harger, H.S. Historical notes on the Geological Society of South Africa. Proceedings of the Geological Society of South Africa, 1939, Vol. 42, pp. lxvii-lxxv.
Journal of the Chemical, Metallurgical and Mining Society of South Africa, 1904/5, Vol. 5, Members; 1940, Vol. 41(1), title page, Past Presidents; 1943, Vol. 43(11 & 12), p. 161, Prodeedings at the annual general meeting.
Long, A.W. The foundation and development of the Astronomical Society of South Africa. Journal of the Astronomical Society of South Africa, January 1930, Vol. 2(4), pp. 153-180.
Malan, M. In quest of health: The South African Institute for Medical Research, 1912-1973. Johannesburg: Lowry, 1988.
Men of the times: Pioneers of the Transvaal and glimpses of South Africa. Transvaal Publishing Company, 1905.
Murray, B.K. Wits, the early years. Johannesburg: Witwatersrand University Press, 1982.
National Automated Archival Information Retrieval System (NAAIRS). http://www.national.archives.gov.za/naairs.htm Documents relating to Kotze, R.N.
Phillips, H. The University of Cape Town, 1918-1948: The formative years. University of Cape Town, 1993.
Ritchie, W. The history of the South African College, 1829-1918. Cape Town: T. Maskew Miller, 1918.
South African Association for the Advancement of Science. Report, 1903, 1905/6, 1908, 1910, 1918: Office bearers and lists of members.
South African Institution of Engineers. Transactions, 1913, Vol. 1, office bearers, and addresses by R.N. Kotze.
South African who's who, 1919/20, 1923/4, 1927/8, 1931/2, 1936, 1939, 1944, 1950.
Transvaal public service list, 1909.
Unie van Zuid-Afrika. Rapport van het Witwatersrand Aardschuddingen Komitee, 1915. Pretoria: Goevernementsdrukkerij, 1916.
Union of South Africa. Public service list, 1914.
University of Cape Town. Honorary degrees awarded. http://www.uct.ac.za/about/honours/degrees/graduates
University of the Cape of Good Hope. Calendar, 1893/4, 1917/8.
University of the Witwatersrand. Honorary Graduates. http://www.wits.ac.za/alumni/alumnirecognition/3600/honorary_degrees.html
Who was who, Vol. 5, 2nd ed. London: Adam & Black, 1964.