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Sharma VS, Geibel JF, Ranney HM.Sharma VS, et al.Proc Natl Acad Sci U S A. 1978 Aug;75(8):3747-50. doi: 10.1073/pnas.75.8.3747.Proc Natl Acad Sci U S A. 1978.PMID: 278985Free PMC article.