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Chee MW, Chuah YM.Chee MW, et al.Proc Natl Acad Sci U S A. 2007 May 29;104(22):9487-92. doi: 10.1073/pnas.0610712104. Epub 2007 May 21.Proc Natl Acad Sci U S A. 2007.PMID: 17517619Free PMC article.