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Grishok A, Hoersch S, Sharp PA.Grishok A, et al.Proc Natl Acad Sci U S A. 2008 Dec 23;105(51):20386-91. doi: 10.1073/pnas.0810589105. Epub 2008 Dec 10.Proc Natl Acad Sci U S A. 2008.PMID: 19073934Free PMC article.