Union of South Africa, Office of Census and Statistics, Report on the Engineering Industry in South Africa 1915/6 to 1923/4, Special Report 31 (Pretoria: Government Printer, 1924).

DOI link for Union of South Africa, Office of Census and Statistics, Report on the Engineering Industry in South Africa 1915/6 to 1923/4, Special Report 31 (Pretoria: Government Printer, 1924).

Union of South Africa, Office of Census and Statistics, Report on the Engineering Industry in South Africa 1915/6 to 1923/4, Special Report 31 (Pretoria: Government Printer, 1924).