Suwarna, Nana, Bambang Hermanto, Torkis Sihombing, and Kusdji Darwin Kusumah. 2006. “Coalbed Methane Potential and Coal Characteristics in the Lati Region, Berau Basin, East Kalimantan”. Indonesian Journal on Geoscience 1 (1):19-30. https://doi.org/10.17014/ijog.1.1.19-30.