RT Journal Article SR Electronic T1 Systematic reviews to evaluate causation: an overview of methods and application JF Evidence Based Medicine JO Evid Based Med FD BMJ Publishing Group Ltd SP 137 OP 141 DO 10.1136/ebmed-2011-100287 VO 17 IS 5 A1 Khan, Khalid S A1 Ball, Elizabeth A1 Fox, Caroline E A1 Meads, Catherine YR 2012 UL http://ebm.bmj.com/content/17/5/137.abstract AB