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Svensson EC, Tufts RL, Polk CE, Leiden JM.Svensson EC, et al.Proc Natl Acad Sci U S A. 1999 Feb 2;96(3):956-61. doi: 10.1073/pnas.96.3.956.Proc Natl Acad Sci U S A. 1999.PMID: 9927675Free PMC article.