Martadi, Setyo Pambudi, and Okki Verdiansyah. “Optimizing of Drill Hole Spacing For Coal Resources Classification in Kelay Blok 3 Area, Labanan Formation, Berau Regency, East Kalimantan”. International Journal of Basic and Applied Sciences 14, no. 8 (January 2, 2026): 667–675. Accessed January 7, 2026. https://www.sciencepubco.com/index.php/IJBAS/article/view/37050.