1. Department of General, Abdominal and Pediatric Surgery, SRH Hospital, Straße des Friedens 122, 07548 Gera, Germany
2. Institute for Quality Assurance in Operative Medicine, Otto-von-Guericke University, 39106 Magdeburg, Germany
3. Municipal Hospital Sachsenhausen, Frankfurt/Main, Germany
4. Friedrich-Alexander University, 91054 Erlangen-Nuremberg, Germany
5. Municipal Hospital, Schwabach, Germany
6. Municipal Hospital, Rostock Suedstadt, Germany
7. Otto-von-Guericke Universität Magdeburg, 39106 Magdeburg, Germany
8. StatConsult, 39112 Magdeburg, Germany