PT - JOURNAL ARTICLE ED - , TI - Purpose and procedure AID - 10.1136/ebm.16.6.e3 DP - 2011 Dec 01 TA - Evidence Based Medicine PG - e3--e3 VI - 16 IP - 6 4099 - http://ebm.bmj.com/content/16/6/e3.short 4100 - http://ebm.bmj.com/content/16/6/e3.full SO - Evid Based Med2011 Dec 01; 16