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Matile P, Cortat M, Wiemken A, Frey-Wyssling A.Matile P, et al. Among authors: frey wyssling a.Proc Natl Acad Sci U S A. 1971 Mar;68(3):636-40. doi: 10.1073/pnas.68.3.636.Proc Natl Acad Sci U S A. 1971.PMID: 5276773Free PMC article.