1. General hospital “Djordje Joanovic”, Department of Internal medicine, Divison of gastroenterology, 5 Bolnicka Dr. Vase Savica St., 23000 Zrenjanin, Serbia
2. Clinic of Gastroenterology and Hepatology, Clinical Center of Serbia, 2 Dr. Koste Todorovica St., 11000 Belgrade, Serbia
3. Mayo Clinic Alix School of Medicine, Rochester, 200 1st St SW, MN 55905, USA
4. Mayo Clinic Health System, 733 W Clairemont Ave Eau Claire, WI 54701, USA
5. Faculty of Medicine, University of Belgrade, 8 Dr. Subotica Starijeg St., 11000 Belgrade, Serbia