ANALISIS HUBUNGAN NILAI HGI (HARDGROVE GRINDABILITY INDEX) ASH CONTENT INHERENT MOISTURE DAN TOTAL SULFUR TERHADAP NILAI KALORI BATUBARA DI PT. GEOSERVICES SAMARINDA KALIMANTAN TIMUR. geo. sci. kut. bas. [Internet]. 2022 Aug. 18 [cited 2025 Sep. 5];5(1):31-7. Available from: https://jurnal.fmipa.unmul.ac.id/index.php/geofis/article/view/789