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Barker WC, Dayhoff MO.Barker WC, et al. Among authors: dayhoff mo.Proc Natl Acad Sci U S A. 1982 May;79(9):2836-9. doi: 10.1073/pnas.79.9.2836.Proc Natl Acad Sci U S A. 1982.PMID: 6283546Free PMC article.