1. School of Medicine, Belgrade + Clinical Center of Serbia, First Surgical Clinic, Clinic for Digestive Surgery, Department for Minimally Invasive Upper Digestive Surgery, Belgrade
2. Clinical Center of Serbia, First Surgical Clinic, Clinic for Digestive Surgery, Department for Minimally Invasive Upper Digestive Surgery, Belgrade
3. Public Health Institute, Šabac
4. School of Medicine, Kosovska Mitrovica
5. School of Medicine, Belgrade