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Johnson GL, Kaslow HR, Bourne HR.Johnson GL, et al. Among authors: bourne hr.Proc Natl Acad Sci U S A. 1978 Jul;75(7):3113-7. doi: 10.1073/pnas.75.7.3113.Proc Natl Acad Sci U S A. 1978.PMID: 277913Free PMC article.