1. Julius Center for Health Sciences and Primary Care University Medical Center Utrecht Utrecht The Netherlands
2. The Dutch Cochrane Centre, Julius Center for Health Sciences and Primary Care University Medical Center Utrecht The Netherlands
3. Department of Epidemiology University of Groningen, University Medical Center Groningen Groningen The Netherlands
4. Department of Hygiene and Epidemiology, School of Medicine University of Ioannina Ioannina Greece
5. Institute of Social and Preventive Medicine University of Bern Bern Switzerland