“UPGRADING OF EAST KALIMANTAN LIGNITE  CHARATERISTICS THROUGH INORGANIC SALT CHEMICAL ACTIVATION TREATMENT PRODUCING MICROWAVE ABSORBENT”. Jurnal Teknologi (Sciences & Engineering) 88, no. 3 (April 30, 2026): 439–446. Accessed September 13, 2026. https://journals.utm.my/jurnalteknologi/article/view/24530.