List of sources:
Agricultural Journal (Union of South Africa), 1911, Vol. 1, paper by Robertson.
Agricultural Journal of the Cape of Good Hope, 1909, Vol. 34, paper by Robertson.
Bullock, A.A. Bibliography of South African botany (up to 1951). Pretoria: Department of Agricultural Technical Services, 1978.
Cape of Good Hope. Report of the Meteorological Commission, 1903, 1904.
Civil service list of the Orange River Colony, 1907, 1910.
Dictionary of South African biography, Vol. 5, 1987.
Keet, J.D.M. Historical review of the development of forestry in South Africa (c. 1972). Electronic copy received from Forestry Scientific/Technical Support, Knysna, January 2011.
National Union Catalogue, pre-1956 imprints. London: Mansell, 1968-1980.
Orange River Colony, Department of Agriculture. Report, 1907/8, 1908/9.
Philosophical Society of the Orange River Colony. Transactions, 1903-1907, Vol. 1, list of members.
Robertson, Colin Charles. CHAH: Council of Heads of Australian Herbaria. Biographical Notes. Retrieved from https://www.anbg.gov.au/biography/robertson-colin-charles.html on 22 June 2020.
South African Association for the Advancement of Science. Report, 1909, 1910, 1918.
South African bibliography to the year 1925. London: Mansell, 1979.
South African Journal of Natural History, 1918, Vol. 1(1), pp. 8-15: Roll of Foundation Members [of the SA Biological Society]; 1920, Vol. 2(2), Roll of Members.
South African Journal of Science, 1927, Vol. 24, paper by Robertson.
Southern African Museums Association Bulletin, 1947, Vol. 4(2), p. 48: [Untitled announcement of Robertson's death].
The late Mr C.C. Robertson. Journal of the South African Forestry Association, 1947, No. 15, pp. 1-2 and 6-7.
Union of South Africa. Public service list, 1914.