1. University Hospital Basel; Institute of Clinical Epidemiology; Hebelstrasse 10 Basel BS Switzerland 4031
2. Inselspital, University of Bern; Department of Visceral and Transplantation Surgery; Ludw. Pav. 5, Inselspital Bern Switzerland 3010
3. Basler Institute for Clinical Epidemiology; Gemeinsamer Bundesausschuss Auf dem Seidenberg 3A Siegburg Germany 53707
4. University Hospital Basel, Switzerland; Clinical Trail Unit; Hebelstrasse 2 Basel Switzerland 4031
5. Kantonsspital Luzern; Department of Surgery; Zürich Switzerland
6. University Hospital Basel (USB); Basel Institute for Clinical Epidemiology; Petersgraben 4 Basel Switzerland CH-4031
7. University Hospital Basel; Institute for Clinical Epidemiology; Hebelstrasse 10, 3rd floor Basel Switzerland CH 4031