“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, vol. 14, no. H1, Apr. 2014, pp. 1-5, https://www.journalofscience.org/index.php/GJSFR/article/view/1275.