M. Iqbal, N. Suwarna, I. Syafri, and W. Winantris, “Eo-Oligocene Oil Shales of the Talawi, Lubuktaruk, and Kiliranjao Areas, West Sumatra: Are they potential source rocks?”, Indonesian J. Geosci., vol. 1, no. 3, pp. 135–149, Dec. 2014.