Iqbal, Rendy Muhamad, et al. “Fabrication and Characterization of Fly Ash-Based Geopolymer and Its Performance for Immobilization of Heavy Metal Cations”. Communications in Science and Technology, vol. 7, no. 2, Dec. 2022, pp. 112-8, doi:10.21924/cst.7.2.2022.868.