Heavy Metal Content of Agricultural Soils in a Tropical Sudan Savannah Area: Katsina State, North-Western Nigeria. Global Journal of Human-Social Science, [S. l.], v. 19, n. B1, p. 43–50, 2019. Disponível em: https://socialscienceresearch.org/index.php/GJHSS/article/view/2837. Acesso em: 19 feb. 2026.