Elijah, L. K., H. M. Junior, and S. A. Ibuteme. “Speciation of Some Heavy Metals in Sediments of the Pennington River, Bayelsa State, Nigeria”. Theory and Applications of Chemistry Vol. 2, July 2019, pp. 93-03, https://stm1.bookpi.org/index.php/tac-v2/article/view/228.