Chia-Chay, Tay, Mohd-Fuad, Syaza-Farzana, Mohd-Nor, Nur-Asma-Diana. “Malachite Green Adsorption Using Industrial Waste Coffee Husk: Isotherm, Kinetic and Response Surface Methodology”. International Journal of Advanced Science and Technology, Vol. 29, no. 04, June 2020, pp. 6439 -55, http://sersc.org/journals/index.php/IJAST/article/view/27333.