1. Department of Surgery, University Hospital Mannheim, Medical Faculty Mannheim, University of Heidelberg, 68167 Mannheim, Germany
2. Department of Surgery, Hospital Boeblingen, 71032 Boeblingen, Germany
3. Institute of Medical Biometry and Statistics, Faculty of Medicine and Medical Center, University of Freiburg, 79104 Freiburg, Germany
4. Institute of Medical Statistics and Biomathematics, Medical Faculty Mannheim, University of Heidelberg, 68167 Mannheim, Germany
5. Library of the Medical Faculty Mannheim, University of Heidelberg, 68167 Mannheim, Germany