Levels of Hexavalent Chromium, Copper, and Total Hardness in Springs and Underground Water in Zanzibar Island. Asian Journal of Applied Sciences, [S. l.], v. 1, n. 5, 2013. Disponível em: https://ajouronline.com/index.php/AJAS/article/view/564. Acesso em: 13 mar. 2025.