1. Pediatric Research Institute The Faculty of Medicine University of Oslo Oslo Norway
2. Department of Chronic Diseases and Ageing Norwegian Institute of Public Health Oslo Norway
3. Department of Pediatrics Østfold Hospital Trust Grålum Norway
4. Lund University Hospital Lund Sweden
5. Center for Child Health Research Tampere University and Department of Pediatrics Tampere University Hospital Tampere Finland
6. The University Consortium of Seinäjoki and Department of Pediatrics Seinäjoki Central Hospital Seinäjoki Finland