1. Institute for Medical Biometry and Statistics; Faculty of Medicine and Medical Center-University of Freiburg; Freiburg im Breisgau Germany
2. Cochrane Germany; Faculty of Medicine and Medical Center-University of Freiburg; Freiburg im Breisgau Germany
3. Population Health Research Institute, St George's; University of London; Cranmer Terrace, London SW17 0RE UK