RT Journal Article SR Electronic T1 Appraising the evidence: what is selection bias? JF Evidence Based Mental Health JO Evid Based Ment Health FD BMJ Publishing Group Ltd, Royal College of Psychiatrists and British Psychological Society SP 67 OP 68 DO 10.1136/ebmh.10.3.67 VO 10 IS 3 A1 Henderson, Max A1 Page, Lisa YR 2007 UL http://ebmh.bmj.com/content/10/3/67.abstract AB