Siregar, Ahmad Marabdi, Chandra A Siregar, and Khairul Umurani. 2024. “Utilization and Experimental Use of Stainless Steel Metal Scrap Machinery Waste, St-40 Iron, Copper and Aluminum to Reduce Co, Hc, Co2 Elements in Vehicle Exhaust”. Jurnal Pendidikan Vokasi Otomotif 6 (2):147-58. https://doi.org/10.21831/jpvo.v6i2.73269.