List of sources:
Cape of Good Hope. Civil service list, 1892.
Cape of Good Hope. Report of the Surveyor-General, 1880.
The Edinburgh Gazette, 20 November 1855, p. 1441. retrieved from https://www.thegazette.co.uk/Edinburgh/issue/6546/page/1442/data.pdf on 17 June 2020.
FamilySearch: Theodor Ferdinand Nicolaus Risler. https://www.familysearch.org/ark:/61903/3:1:3Q9M-CSQ8-H9LR-S?view=index&personArk=/ark:/61903/1:1:QPS2-7TFM&action=view&cc=2517051&lang=en&groupId=
General directory and guide-book to the Cape of Good Hope and its dependencies, 1886, p. 111, 202.
Heese, J.A. South African genealogies. Pretoria and Stellenbosch, 1986-2005.
National Automated Archival Information Retrieval System (NAAIRS). http://national.archives.gov.za/naairs.htm Documents relating to Risler, Theodore / Risler, Theodor / Risler, T.
South African bibliography to the year 1925. London: Mansell, 1979.
South African Philosophical Society. Transactions, 1877-1881, Vol. 1 and 2: Lists of members.