1. Department of Gastroenterology, Frankenwaldklinik, Kronach, Germany
2. Department of Gastroenterology, Hospital Universitario Infanta Leonor, Madrid, Spain
3. Department of Gastroenterology, Hospital of the Ministry of the Interior, Szcezcin, Poland
4. University of Belgrade, Belgrade, Serbia
5. Ameos Klinikum Otto-von-Guericke University Teaching Hospital, Halberstadt, Germany