2022. ANALISIS HUBUNGAN NILAI HGI (HARDGROVE GRINDABILITY INDEX) ASH CONTENT INHERENT MOISTURE DAN TOTAL SULFUR TERHADAP NILAI KALORI BATUBARA DI PT. GEOSERVICES SAMARINDA KALIMANTAN TIMUR. GEOSAINS KUTAI BASIN. 5, 1 (Aug. 2022), 31–37. DOI:https://doi.org/10.30872/geofisunmul.v5i1.789.