Rosli, Mohd Arif, Zawawi Daud, Halizah Awang, Nur Adila Ab Aziz, Mohd Baharudin Ridzuan, Mahmoud Hijab Abubakar, Mohd Shalahuddin Adnan, and Husnul Azan Tajarudin. “Adsorption Efficiency and Isotherms of COD and Color Using Limestone and Zeolite Adsorbents”. International Journal of Integrated Engineering 10, no. 8 (December 29, 2018). Accessed October 1, 2020. https://publisher.uthm.edu.my/ojs/index.php/ijie/article/view/2358.