Mayasari, Windi, Hery Suhartoyo, and Zainal Muktamar. “PERSEPSI PEKERJA TAMBANG BATUBARA PT. FIRMAN KETAUN”. Naturalis: Jurnal Penelitian Pengelolaan Sumber Daya Alam dan Lingkungan 8, no. 1 (October 14, 2019): 9–14. Accessed May 9, 2024. https://ejournal.unib.ac.id/naturalis/article/view/9157.