1. Fuel Cell Technologies Program Record: Fuel Cell Bus Targets;U.S.DOE,2012
2. Ballard. Transp. London fuel cell bus achieves 20,000 hours oper. http//ballard.com/about-Ballard/newsroom/fuel-Cell-Market-updates/2015/TfL_Mileage.aspx (n.d.).
3. Status of hydrogen fuel cell electric buses worldwide
4. National Renewable Energy Laboratory Technology Validation;U.S. DOE,2015
5. Fuel Cell Bus Exceed. 20,000 Hours Serv;AC TRANSIT,2016