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Ahlgren SC, Thakur V, Bronner-Fraser M.Ahlgren SC, et al.Proc Natl Acad Sci U S A. 2002 Aug 6;99(16):10476-81. doi: 10.1073/pnas.162356199. Epub 2002 Jul 24.Proc Natl Acad Sci U S A. 2002.PMID: 12140368Free PMC article.