Analisis Proksimat dan Ultimat Terhadap Total Sulfur dan Nilai Kalori pada Batubara (PT Geoservices Samarinda). GEOSAINS KUTAI BASIN, [S. l.], v. 6, n. 2, p. 126–136, 2023. DOI: 10.30872/geofisunmul.v6i2.1145. Disponível em: https://jurnal.fmipa.unmul.ac.id/index.php/geofis/article/view/1145. Acesso em: 10 oct. 2025.