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Tan WS, Ding YY, Chong WF, Tay JC, Tan JY.Tan WS, et al. Among authors: ding yy.BMC Health Serv Res. 2012 May 14;12:115. doi: 10.1186/1472-6963-12-115.BMC Health Serv Res. 2012.PMID: 22583538Free PMC article.