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O'Brien WA, Hartigan PM, Daar ES, Simberkoff MS, Hamilton JD.O'Brien WA, et al. Among authors: daar es.Ann Intern Med. 1997 Jun 15;126(12):939-45. doi: 10.7326/0003-4819-126-12-199706150-00002.Ann Intern Med. 1997.PMID: 9182470Clinical Trial.