PT - JOURNAL ARTICLE ED - , TI - Purpose and procedure AID - 10.1136/ebm1027 DP - 2010 Apr 01 TA - Evidence Based Medicine PG - 35--35 VI - 15 IP - 2 4099 - http://ebm.bmj.com/content/15/2/35.short 4100 - http://ebm.bmj.com/content/15/2/35.full SO - Evid Based Med2010 Apr 01; 15