“Optimization of Pretreatment and Hydrothermal Process of Na-X Zeolite from Kaolin and Metakaolin”. Jurnal Kimia Valensi 5, no. 2 (November 30, 2019): 202–210. Accessed October 14, 2025. https://journal.uinjkt.ac.id/valensi/article/view/11326.