Nasir, M., H. Febriano, and B. Balisranislam. “Effect of the Using of Racing Exhaust With Variation Soundproofing Material Against Exhaust Emissions and Noise on 4 Stroke Motorcycle”. MOTIVECTION : Journal of Mechanical, Electrical and Industrial Engineering, Vol. 3, no. 3, Sept. 2021, pp. 135-42, doi:10.46574/motivection.v3i3.95.