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Clarke CA, Miller T, Chang ET, Yin D, Cockburn M, Gomez SL.Clarke CA, et al.Soc Sci Med. 2010 May;70(9):1373-80. doi: 10.1016/j.socscimed.2010.01.003. Epub 2010 Feb 12.Soc Sci Med. 2010.PMID: 20171001Free PMC article.