ENGELBRECHT, W.G. VALUING THE ECONOMIC COSTS AND BENEFITS OF CLEAN AIR. Clean Air Journal, [S. l.], v. 8, n. 5, p. 9–11, 1992. DOI: 10.17159/caj/1992/8/5.7122. Disponível em: https://cleanairjournal.org.za/article/view/7122. Acesso em: 8 may. 2024.