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Helfand M; U.S. Preventive Services Task Force.Helfand M, et al.Ann Intern Med. 2004 Jan 20;140(2):128-41. doi: 10.7326/0003-4819-140-2-200401200-00015.Ann Intern Med. 2004.PMID: 14734337Free article.Review.
Chou R, Clark EC, Helfand M; U.S. Preventive Services Task Force.Chou R, et al. Among authors: helfand m.Ann Intern Med. 2004 Mar 16;140(6):465-79. doi: 10.7326/0003-4819-140-6-200403160-00014.Ann Intern Med. 2004.PMID: 15023713Free article.Review.