Yusoff, H., N. M. Sulaiman, and M. Kheireddine Aroua. “Ultra Filtration Using Gas Sparging Technique for Treatment of Natural Rubber Effluent”. Malaysian Journal of Science, vol. 23, Dec. 2004, pp. 177-84, https://samudera.um.edu.my/index.php/MJS/article/view/9052.