Situmorang, Humala. “The Effect of the Ban on Nickel Exports on the Economic Profitability of PT Vale Indonesia, Tbk from 2015 - June 2020.”. Fundamental Management Journal 6, no. 1 (April 29, 2021): 73 - 82. Accessed May 3, 2024. http://ejournal.uki.ac.id/index.php/jm/article/view/2834.