WALKER, N.P. The use of diffusion tubes to measure NO₂ in South Africa. Clean Air Journal, [S. l.], v. 7, n. 4, 1987. DOI: 10.17159/caj/1987/7/4.7289. Disponível em: https://cleanairjournal.org.za/article/view/7289. Acesso em: 7 may. 2024.