Soedjono, Eddy S. “Study on Communal Wastewater Treatment Plants (CWWTPs) in Gresik, Indonesia”. International Journal of Integrated Engineering 11, no. 2 (May 6, 2019). Accessed April 7, 2026. https://penerbit.uthm.edu.my/ojs/index.php/ijie/article/view/4269.