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Tudor-Locke C, Burkett L, Reis JP, Ainsworth BE, Macera CA, Wilson DK.Tudor-Locke C, et al.Prev Med. 2005 Mar;40(3):293-8. doi: 10.1016/j.ypmed.2004.06.003.Prev Med. 2005.PMID: 15533542Clinical Trial.