Jamaludin, Jamaludin, dan Septiana Widi Astuti. “Kajian Biaya Operasi Kereta Api”. Jurnal Perkeretaapian Indonesia (Indonesian Railway Journal) 2, no. 1 (Maret 20, 2018): 56–65. Diakses Juni 4, 2026. https://jurnal.ppi.ac.id/jpi/article/view/46.