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Blomhoff R, Berg T, Norum KR.Blomhoff R, et al. Among authors: norum kr.Proc Natl Acad Sci U S A. 1988 May;85(10):3455-8. doi: 10.1073/pnas.85.10.3455.Proc Natl Acad Sci U S A. 1988.PMID: 3368453Free PMC article.