Mustapha, A. A, Abdu, N., Oyinlola, E. Y, Nuhu, A. A, and Dawaki, M. U. “Distribution of Aluminium, Iron, Calcium, Magnesium and Manganese in the Soils of Savannah Region of Northern Nigeria”. Journal of Agricultural Economics, Environment and Social Sciences, Vol. 6, no. 1, July 2020, pp. 32-39, https://jaeess.com.ng/index.php/jaeess/article/view/36.