G. Hayder, and L. L. Guan. “Evaluation of Bio-Carrier in Attached Growth Wastewater Treatment System”. Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, vol. 19, no. 1, Mar. 2016, pp. 10-14, https://semarakilmu.com.my/journals/index.php/fluid_mechanics_thermal_sciences/article/view/2583.