List of sources:
Chemical and Metallurgical Society of South Africa. Proceedings, 1894-1899, Vol. 1-2.
Chemical, Metallurgical and Mining Society of South Africa. Proceedings, (1902-1903, Vol. 3; Journal, 1904-1906, Vol. 5-6, Members, office bearers and council; 1934, Vol. 34, pp. 279-318, 40th anniversary; 1941, Vol. 41, pp. 477-478, Obituary, John R. Williams.
FamilySearch: John Richard Williams. https://ancestors.familysearch.org/en/LT5N-VK8/john-richard-williams-1862-1941
Johnson, E.H. South African metallurgy. In W. Flint & J.D.F. Gilchrist (eds), Science in South Africa (pp. 310-317). Cape Town: T. Maskew Miller, 1905.
National Archives Repository (TAB), Source MHG, Vol. 0, Ref. 2344/41: death notice, John Richard Williams.
National Automated Archival Information Retrieval System (NAAIRS). http://national.archives.gov.za/naairs.htm Documents relating to Williams, John Richard.
National Union Catalogue, pre-1956 imprints. London: Mansell, 1968-1980.
Orr, J. Presidential address. Associated Scientific and Technical Societies of South Africa, Annual Proceedings, 1938, pp. 15-86.
Rosenthal, E. Southern African dictionary of national biography. London: F. Warne, 1966.
South African Association for the Advancement of Science. Report, 1903, 1904.
South African bibliography to the year 1925. London: Mansell, 1979.
University of the Cape of Good Hope. Calendar, 1899/1900, 1902/3, 1903/4, 1906/7.