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Barton MC, Shapiro DJ.Barton MC, et al. Among authors: shapiro dj.Proc Natl Acad Sci U S A. 1988 Oct;85(19):7119-23. doi: 10.1073/pnas.85.19.7119.Proc Natl Acad Sci U S A. 1988.PMID: 3174624Free PMC article.