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Hughes WO, Sumner S, Van Borm S, Boomsma JJ.Hughes WO, et al.Proc Natl Acad Sci U S A. 2003 Aug 5;100(16):9394-7. doi: 10.1073/pnas.1633701100. Epub 2003 Jul 23.Proc Natl Acad Sci U S A. 2003.PMID: 12878720Free PMC article.