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Lindahl L, Zengel JM.Lindahl L, et al. Among authors: zengel jm.Proc Natl Acad Sci U S A. 1979 Dec;76(12):6542-6. doi: 10.1073/pnas.76.12.6542.Proc Natl Acad Sci U S A. 1979.PMID: 160567Free PMC article.