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Ward AJ, Sumpter DJ, Couzin ID, Hart PJ, Krause J.Ward AJ, et al. Among authors: krause j.Proc Natl Acad Sci U S A. 2008 May 13;105(19):6948-53. doi: 10.1073/pnas.0710344105. Epub 2008 May 12.Proc Natl Acad Sci U S A. 2008.PMID: 18474860Free PMC article.