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Nyarko KA, Lopez-Camelo J, Castilla EE, Wehby GL.Nyarko KA, et al.Am J Public Health. 2013 Sep;103(9):1675-84. doi: 10.2105/AJPH.2012.301021. Epub 2013 Feb 14.Am J Public Health. 2013.PMID: 23409894Free PMC article.