1. Greenhouse gas emissions standards for passenger vehicles, https://www.greencarcongress.com/2019/04/20190416-gdi.html. The International Council on Clean Transporation; 2017.
2. Extreme Downsizing of CNG Engines-Opportunities and Challenges;Kramer,2014
3. Alternative fuels for road vehicles;Poulton,1994
4. Pischinger S, Umierski M, Hüchtebrock B. New CNG Concepts for Passenger Cars: High Torque Engines with Superior Fuel Consumption. SAE Technical Paper. SAE International; 2003.
5. The effects of compression ratio on nitric oxide and hydrocarbon emissions from a spark-ignition natural gas fuelled engine;Takagaki;SAE Trans,1997