Widayat, A. H., Anggayana, K., & Khoiri, I. (2015). Precipitation of Calcite during the Deposition of Paleogene Sangkarewang Oil Shale, Ombilin Basin, West Sumatra, Indonesia. Indonesian Journal on Geoscience, 2(3), 185–197. https://doi.org/10.17014/ijog.2.3.185-197