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Rees-Clayton E, Montgomery JP, Enger KS, Boulton ML.Rees-Clayton E, et al. Among authors: boulton ml.Am J Public Health. 2012 Sep;102(9):1735-41. doi: 10.2105/AJPH.2011.300577. Epub 2012 Jul 19.Am J Public Health. 2012.PMID: 22813091Free PMC article.