URL dokumen:
https://prisma.simaster.ugm.ac.id/karya_files/metals-and-chemical-compounds-contaminants-in-diesel-engine-lubricant-with-b20-and-b100-biofuels-for-long-term-operation-dcfcd07e645d245babe887e5e2daa016/bf77fbad-9146-11eb-8284-e4434b0aade8