1. Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford OX1 2JD, UK
2. Psychology, University of Southampton, Southampton SO17 1BJ, UK
3. Belgian Health Care Knowledge Centre (KCE), Brussels B-1000, Belgium
4. Bodleian Health Care Libraries, University of Oxford, Oxford OX1 2JD, UK
5. Faculty of Medicine, Vilnius University, Vilnius LT-03101, Lithuania