1. Medical Simulation Training Center Research Institute at Medical University of Plovdiv, 4000 Plovdiv, Bulgaria
2. Department of Gastroenterology, Pulmed University Hospital, 4000 Plovdiv, Bulgaria
3. Department of Surgery, Pulmed University Hospital, 4000 Plovdiv, Bulgaria
4. Second Department of Internal Medicine, Medical University of Plovdiv, 4000 Plovdiv, Bulgaria
5. Department of Gastroenterology, Kaspela University Hospital, 4001 Plovdiv, Bulgaria