Yang, Z. , Li, J. , Xie, Z. , Ling, J. , Wang, J. , Li, M.. "Real-World PM, PN and NOx Emission Differences among DOC+CDPF Retrofit Diesel-, Diesel- and Natural Gas-Fueled Buses". World Academy of Science, Engineering and Technology, Open Science Index 188, International Journal of Energy and Power Engineering (2022), 16(8), 113 - 117.