Venter, Andrew, Ville Vakkar, Johan Beukes, Pieter van Zyl, Heikki Laakso, Desmond Mabaso, Petri Tiitta, et al. 2012. “An Air Quality Assessment in the Industrialised Western Bushveld Igneous Complex, South Africa”. South African Journal of Science 108 (9/10):10 Pages. https://sajs.co.za/article/view/9791.