Houreld, W., and N. Legge. “Vermindering Van Rookuitlating in Siersteenproduksie - Suksesvol Gedemonstreer, En Gebaseer Op Bekende Maar Half-Vergete Beginsels”. Clean Air Journal 1, no. 02 (December 3, 1972): 5–10. Accessed May 17, 2024. https://cleanairjournal.org.za/article/view/7396.