Sukmilin, A., and R. Sangsirimongkolying. “Removal of Iron from Groundwater by Ozonation: The Response Surface Methodology for Parameter Optimization: 10.32526/Ennrj/19/2020286”. Environment and Natural Resources Journal, vol. 19, no. 4, June 2021, pp. 330-6, https://ph02.tci-thaijo.org/index.php/ennrj/article/view/242621.