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Schmitt MP, Twiddy EM, Holmes RK.Schmitt MP, et al. Among authors: holmes rk.Proc Natl Acad Sci U S A. 1992 Aug 15;89(16):7576-80. doi: 10.1073/pnas.89.16.7576.Proc Natl Acad Sci U S A. 1992.PMID: 1502169Free PMC article.