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Povirk LF, Goldberg IH.Povirk LF, et al. Among authors: goldberg ih.Proc Natl Acad Sci U S A. 1982 Jan;79(2):369-73. doi: 10.1073/pnas.79.2.369.Proc Natl Acad Sci U S A. 1982.PMID: 6210907Free PMC article.