RT Journal Article SR Electronic T1 Clopidogrel plus aspirin was inferior to oral anticoagulation for preventing vascular events in atrial fibrillation JF Evidence Based Medicine JO Evid Based Med FD BMJ Publishing Group Ltd SP 170 OP 170 DO 10.1136/ebm.11.6.170 VO 11 IS 6 YR 2006 UL http://ebm.bmj.com/content/11/6/170.abstract AB