VAN GRAAN, J.; POTGIETER, W.; LLOYD, S. Air pollution in the Vaal Triangle - plans for the future. Clean Air Journal, [S. l.], v. 8, n. 7, 1993. DOI: 10.17159/caj/1993/8/7.7310. Disponível em: https://cleanairjournal.org.za/article/view/7310. Acesso em: 28 jan. 2022.