1. Departement of General Surgery, Cantonal Hospital Lucerne, P.O. Box 6000; Spitalstrasse 16, CH-6000 Luzern, Switzerland
2. Departement of General Surgery, St. Mary's Hospital Okpoga. P.O Box 36, Okpoga, Benue State, Nigeria
3. Department of Surgery, Lachen Hospital, Oberdorfstrasse 41, CH-8853 Lachen, Switzerland