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Chen X, Li G, Unger JB, Liu X, Johnson CA.Chen X, et al.Am J Public Health. 2003 Dec;93(12):2099-104. doi: 10.2105/ajph.93.12.2099.Am J Public Health. 2003.PMID: 14652341Free PMC article.
Chen X, Unger JB, Palmer P, Weiner MD, Johnson CA, Wong MM, Austin G.Chen X, et al.Addict Behav. 2002 Sep-Oct;27(5):799-817. doi: 10.1016/s0306-4603(01)00211-8.Addict Behav. 2002.PMID: 12201385
Shakib S, Zheng H, Johnson CA, Chen X, Sun P, Palmer PH, Yan L, Jie G, Unger JB.Shakib S, et al. Among authors: chen x.Prev Med. 2005 Jan;40(1):83-91. doi: 10.1016/j.ypmed.2004.05.029.Prev Med. 2005.PMID: 15530584
Zheng H, Sussman S, Chen X, Wang Y, Xia J, Gong J, Liu C, Shan J, Unger J, Johnson CA.Zheng H, et al. Among authors: chen x.Addict Behav. 2004 Dec;29(9):1725-33. doi: 10.1016/j.addbeh.2004.03.035.Addict Behav. 2004.PMID: 15530717