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Sheen FM, Levis RW.Sheen FM, et al.Proc Natl Acad Sci U S A. 1994 Dec 20;91(26):12510-4. doi: 10.1073/pnas.91.26.12510.Proc Natl Acad Sci U S A. 1994.PMID: 7809068Free PMC article.