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Vaux DL, Strasser A.Vaux DL, et al.Proc Natl Acad Sci U S A. 1996 Mar 19;93(6):2239-44. doi: 10.1073/pnas.93.6.2239.Proc Natl Acad Sci U S A. 1996.PMID: 8637856Free PMC article.Review.