1. Department of Otorhinolaryngology–Head and Neck Surgery, University Medicine Mannheim, University of Heidelberg, Mannheim, Germany
2. Department of Otorhinolaryngology–Head and Neck Surgery, University Hospital of Schleswig-Holstein, Lübeck, Germany
3. Department of Otolaryngology–Head and Neck Surgery, School of Medicine, Johns Hopkins University, Baltimore, Maryland
4. Institute of Medical Biometry and Statistics, Faculty of Medicine and Medical Center–University of Freiburg, Freiburg, Germany
5. Institute for Evidence in Medicine (for Cochrane Germany Foundation), Medical Center–University of Freiburg, Freiburg, Germany