1. The Medical University of Warsaw; Warsaw; Poland
2. Umeå University; Umeå; Sweden
3. Referral Center for Paediatric Gastroenterology & Nutrition; Children's Hospital Zagreb; Zagreb; Croatia
4. University of Munich Medical Centre; Munich; Germany
5. Leiden University Medical Center; Leiden; The Netherlands
6. Sackler Faculty of Medicine; Tel-Aviv University; Tel-Aviv; Israel
7. University Federico II; Naples; Italy