B. A. Br Siburian, R. H. Lubis, and H. Sipahutar, “The Effect of Operational Costs on Sales at Mujur Jaya Photocopy Business in Pandan, Central Tapanuli Regency”, JEMA, vol. 3, no. 01, pp. 87–91, Mar. 2026, Accessed: Mar. 17, 2026. [Online]. Available: https://jurnal.devitara.or.id/index.php/ekonomi/article/view/345