List of sources:
Cape of Good Hope. Catalogue of the natural history collections of the Albany Museum, Grahamstown (Appendix to Parliamentary Report G24-'83). Cape Town: W.A. Richards & Sons, 1883.
Cape of Good Hope. Report of the Acting Surveyor-General for the year 1879.
Cape of Good Hope almanac and annual register... (title varies), 1857, 1865 and 1886: Sworn land surveyors.
Dictionary of South African biography, Vol. 3, 1977.
Francis Henry Samuel Orpen. Geni. Retrieved from https://www.geni.com/people/Francis-Orpen/6000000019008464371
on 2019-1-16.
Francis Henry Samuel Orpen. Monthly Notices of the Royal Astronomical
Society, 1894, Vol. 54(4), p. 195. Retrieved from https://academic.oup.com/mnras/article/54/4/195/1070784
on 2019-1-16.
Heese, J.A. South African genealogies. Pretoria and Stellenbosch, 1986-2005.
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 Orpen, Francis Henry Samuel / Orpen, Francis H.S. / Orpen, Francis / Orpen, F.H.S.
South African bibliography to the year 1925. London: Mansell, 1979.
Stevenson, M. A forgotten Eastern Cape frontier artist: Richard John Newenham Orpen. Quarterly Bulletin of the South African Library, 1997, Vol. 51(4), pp. 161-164.