1. Swiss Association of Laparoscopic and Thoracoscopic Surgery (SALTS) Study Group, Zurich, Switzerland
2. Department of Surgery, Lindenhof Hospital, University of Berne, Berne, Switzerland
3. Department of Surgery, Kantonsspital Bruderholz, Binningen, Switzerland
4. Department of Abdominal and Oncological Surgery, Hôpital de la Timone, Marseilles, France
5. Institute of Mathematical Statistics and Actuarial Science, University of Berne, Berne, Switzerland
6. Clinical Pharmacology and Toxicology, University Hospital of Basle, Basle, Switzerland