1. Section of Pediatric Surgery, Oslo University Hospital, Rikshospitalet, University of Oslo, Oslo, Norway
2. Department of Pediatric Surgery, Hospital for Children and Adolescents, University of Helsinki, Helsinki, Finland
3. Department of Pediatric Surgery, The Queen Silvia Children's Hospital, Gothenburg, Sweden
4. Department of Pediatrics, Astrid Lindgren Children's Hospital, Stockholm, Sweden
5. Department of Pediatrics, Oslo universitetssykehus, Rikshospitalet, University of Oslo, Oslo, Norway
6. Department of Pediatric Surgery, Karolinska University Hospital, Stockholm, Sweden