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Ricketts TH, Daily GC, Ehrlich PR, Michener CD.Ricketts TH, et al. Among authors: michener cd.Proc Natl Acad Sci U S A. 2004 Aug 24;101(34):12579-82. doi: 10.1073/pnas.0405147101. Epub 2004 Aug 11.Proc Natl Acad Sci U S A. 2004.PMID: 15306689Free PMC article.