The research team of EMISIA and the Environmental Protection Department of Hong Kong have published their recent study:
Papadopoulos G, Ntziachristos L, Tziourtzioumis C, Keramydas C, Lo T-S, Ng K-L, Wong H-LA and Wong CK-L (2020). Real-world gaseous and particulate emissions from Euro IV to VI medium duty diesel trucks. Science of The Total Environment, Volume 31. https://doi.org/10.1016/j.scitotenv.2020.139137.
The article may be accessed from here.