1. Department of Pediatrics, Beatrix Children's Hospital; University Medical Centre Groningen; Groningen the Netherlands
2. Department of Sports Medicine; Hospital De Tjongerschans; Heerenveen the Netherlands
3. Department of Respiratory Medicine and Allergology; Skane University Hospital; Lund Sweden
4. Department of Clinical Pharmacy and Pharmacology and Department of General Practice; University Medical Centre Groningen; Groningen the Netherlands
5. Department of Pediatrics; Medisch Spectrum Twente; Enschede the Netherlands