Michael Udoidiong, O. ., B. . Julius Oribhabor, E. . Effiong Munam, and J. . James Bernard. “Assessment of the Impact of Human Settlement on the Heavy Metal Concentrations of Lower Cross River, Nigeria”. Scientific Journal of Pure and Applied Sciences, vol. 2, no. 7, July 2013, pp. 270-8, http://sjournals.com/index.php/sjpas/article/view/970.