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Sisson SD, Casagrande SS, Dalal D, Yeh HC; Johns Hopkins University School of Medicine.Sisson SD, et al.BMC Med Educ. 2011 Jun 8;11:30. doi: 10.1186/1472-6920-11-30.BMC Med Educ. 2011.PMID: 21651768Free PMC article.