Javed, T., F. A. Awan, M. Arshad, A. Mashiatullah, F. J. Iftikhar, and S. N. Khan. “REMOVAL OF CADMIUM, COPPER, LEAD AND ZINC FROM SIMULATED INDUSTRIAL EFFLUENTS USING SILICA POWDER”. The Nucleus, vol. 50, no. 2, May 2013, pp. 135-40, http://202.83.167.189/index.php/Nucleus/article/view/763.