1. Department of General, Visceral and Oncological Surgery, Helios University Hospital Wuppertal, University of Witten/Herdecke
2. Ev. Krankenhaus Lippstadt
3. Helios St. Elisabeth Klinik Oberhausen
4. Helios Klinikum Duisburg
5. Helios Klinikum Niederberg
6. Helios Klinikum Schwerin
7. Institute for Research in Operative Medicine (IFOM), University of Witten/Herdecke, Germany