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Collins A, Keats BJ, Dracopoli N, Shields DC, Morton NE.Collins A, et al. Among authors: keats bj.Proc Natl Acad Sci U S A. 1992 May 15;89(10):4598-602. doi: 10.1073/pnas.89.10.4598.Proc Natl Acad Sci U S A. 1992.PMID: 1584796Free PMC article.