RT Journal Article SR Electronic T1 Haynes RB, Sackett DL, Guyatt GH, et al. Clinical epidemiology: how to do clinical practice research. 3rd edition. Philadelphia, PA: Lippincott Williams & Wilkins, 2006. JF Evidence Based Medicine JO Evid Based Med FD BMJ Publishing Group Ltd SP 124 OP 125 DO 10.1136/ebm.11.4.124 VO 11 IS 4 A1 Carl Heneghan YR 2006 UL http://ebm.bmj.com/content/11/4/124.abstract AB