Anggara, Ferian, Himawan T.B.M. Petrus, Aulia Agus Patria, and Aya Shika Bangun. 2020. “Preliminary Study of Rare Earth Element and Yttrium (REY) Content of Coal In Sangatta Coalfield, East Kalimantan, Indonesia”. Indonesian Journal on Geoscience 7 (3):305-14. https://doi.org/10.17014/ijog.7.3.305-314.