“Removal of Cu+2, Zn+2 and Cd+2 from Aqueous Solution by Using Ion Exchanger Derived from Sack Polypropylene Grafted with Maleic Acid and its Derivatives”, RSCI, vol. 23, no. 5, pp. 115–127, Jul. 2012, doi: 10.33899/rjs.2012.60006.