List of sources:
Chemical and Metallurgical Society of South Africa. Proceedings, 1894-1899, Vol. 1, lists of members and office bearers; Vol. 2, pp. 358-362, Fourth annual meeting; pp. 836-847, Notes and comments.
Chemical, Metallurgical and Mining Society of South Africa. Proceedings, 1902-1903, Vol. 3, list of members; Journal, 1904/5, Vol. 5, Members; 1934, Vol. 34(9), pp. 279-318, 40th anniversary; 1938, Vol. 38, pp. 437 and 472, Obituary; 1940, Vol. 41(1), p. 1, list of presidents.
FamilySearch: William Robert Feldtmann. https://www.familysearch.org/ark:/61903/3:1:3Q9M-C91Q-Q37Q-4?view=index&personArk=/ark:/61903/1:1:QGJ5-PQCV&action=view
Fora dyskusyjne: William
Robert Feldtmann. http://boards.ancestry.pl/thread.aspx?mv=flat&m=2&p=surnames.feldtmann
Retrieved on 31 October 2016.
Geological Society of South Africa. Transactions, 1897, Vol. 2, list of members.
Orr, J. Presidential address. Associated Scientific and Technical Societies of South Africa, Annual Proceedings, 1938, pp. 15-86.
Royal Society of London. Catalogue of scientific papers [1800-1900]. London: Royal Society, 1867-1925.
South African bibliography to the year 1925. London: Mansell, 1979.