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Sands MS, Birkenmeier EH.Sands MS, et al.Proc Natl Acad Sci U S A. 1993 Jul 15;90(14):6567-71. doi: 10.1073/pnas.90.14.6567.Proc Natl Acad Sci U S A. 1993.PMID: 8101990Free PMC article.