risano, yudi. 2022. “Utilization of Natural Zeolites and Fly Ash (Coal) Mixture Physically Activated Using Furnace As A Pellet - Shaped Air Filter To Increase Engine Torque, Tecumseh TD110. 4-Stroke Petrol Motor”. Journal of Engineering and Scientific Research 4 (1):14-17. https://doi.org/10.23960/jesr.v4i1.99.