James, M. O., and P. O. Okolo. “?VARIATION OF HEAVY METAL CONCENTRATIONS IN WATER AND FRESHWATER FISH IN NIGER DELTA WATERS - A CASE STUDY OF BENIN RIVER”. Biological Sciences - PJSIR, vol. 46, no. 6, Dec. 2003, pp. 439-42, https://v2.pjsir.org/index.php/biological-sciences/article/view/1697.