Endri, Endri, Andyan Pradipta Utama, Aminudin Aminudin, Maya Syafriana Effendi, Bambang Santoso, and Achmad Bahiramsyah. “Coal Price and Profitability: Evidence of Coal Mining Companies in Indonesia”. International Journal of Energy Economics and Policy 11, no. 5 (August 20, 2021): 363–368. Accessed February 4, 2023. https://econjournals.com/index.php/ijeep/article/view/11503.