Garba, Akan, and J. C. 2014. “Spatial Distribution of the Heavy Metals: Ni, Fe, Cr, and Mn in Roadside Soils of Maiduguri Metropolis, Borno State Nigeria”. Global Journal of Science Frontier Research 14 (H1):1-5. https://journalofscience.org/index.php/GJSFR/article/view/1275.