Ho, K., Ho, S.S.H., Huang, R., Liu, S., Cao, J., Zhang, T., Chuang, H., Chan, C., Hu, D., Tian, L. (2015). Characteristics of water-soluble organic nitrogen in fine particulate matter in the continental area of China, Atmospheric Environment, 106, 252-261, 10.1016/j.atmosenv.2015.02.010