Ayodele J.T., and Mohammed S. S. 2011. “Comparative Techniques for Extraction of Ni, Cu, Zn and Pb in Guinea Corn Fields of Kaduna Metropolis, Nigeria”. International Journal of Research in Chemistry and Environment (IJRCE) 1 (1):142-46. https://ijrce.org/index.php/ijrce/article/view/69.