Cao, J. J., Chow, J. C., Lee, S. C., Li, Y., Chen, S. W., An, Z. S., Fung, K. K., Watson, J. G., Zhu, C. S., Liu, S. X. (2005). Characterization and source apportionment of atmospheric organic and elemental carbon during Fall and Winter 2003 in Xi’an, China, Atmos Chem Phys Discuss, 5, 3561-3593