SUWARNA, Nana; HERMANTO, Bambang. Berau coal in East Kalimantan; Its petrographics characteristics and depositional environment. Indonesian Journal on Geoscience, [S. l.], v. 2, n. 4, p. 191–206, 2007. DOI: 10.17014/ijog.2.4.191-206. Disponível em: https://ijog.geologi.esdm.go.id/index.php/IJOG/article/view/38. Acesso em: 5 may. 2025.