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Boylan JA, Posey JE, Gherardini FC.Boylan JA, et al.Proc Natl Acad Sci U S A. 2003 Sep 30;100(20):11684-9. doi: 10.1073/pnas.2032956100. Epub 2003 Sep 15.Proc Natl Acad Sci U S A. 2003.PMID: 12975527Free PMC article.