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Urdea MS, Merryweather JP, Mullenbach GT, Coit D, Heberlein U, Valenzuela P, Barr PJ.Urdea MS, et al. Among authors: barr pj.Proc Natl Acad Sci U S A. 1983 Dec;80(24):7461-5. doi: 10.1073/pnas.80.24.7461.Proc Natl Acad Sci U S A. 1983.PMID: 6369317Free PMC article.