1. The Medical University of Warsaw; Warsaw Poland
2. Sackler Faculty of Medicine; Tel-Aviv University; Tel-Aviv Israel
3. University Federico II; Naples Italy
4. Epidemiology and Global Health Unit; Department of Public Health and Clinical Medicine; Umeå University; Umeå Sweden
5. Referral Center for Paediatric Gastroenterology & Nutrition; Children's Hospital Zagreb; Zagreb Croatia
6. University of Munich Medical Centre; Munich Germany
7. Heim Pál Children's Hospital; Budapest Hungary
8. Leiden University Medical Center; Leiden The Netherlands
9. Pediatric Gastroenterology and Hepatology; La Fe University Hospital; Valencia Spain