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Wood, Lesley; Egger, Matthias; Gluud, Lise Lotte; Schulz, Kenneth F; Jüni, Peter; Altman, Douglas G; Gluud, Christian; Martin, Richard M; Wood, Anthony J G; Sterne, Jonathan A C (2008). Empirical evidence of bias in treatment effect estimates in controlled trials with different interventions and outcomes: meta-epidemiological study. BMJ, 336(7644), pp. 601-5. London: BMJ Publishing Group 10.1136/bmj.39465.451748.AD