Hanifah, Rahmatul, et al. “SYNTHESIS OF SODALITE ZEOLITE FROM COAL BOTTOM ASH WITH VARIATION OF NaAlO2 CONCENTRATION USING ALKALI MELTING HYDROTHERMAL METHOD”. Spektra: Jurnal Fisika Dan Aplikasinya, vol. 3, no. 3, Dec. 2018, pp. 167-72, https://journal.unj.ac.id/unj/index.php/spektra/article/view/8652.