1. Department of Pediatrics, Friedrich Schiller University of Jena, Jena, Germany
2. Department of Pediatrics, Justus Liebig University Giessen, Giessen, Germany
3. Pediatric Practice, Herford, Germany
4. Department of Pediatrics, University of Leipzig, Leipzig, Germany
5. Helios Children's Hospital, Erfurt, Germany
6. Department of Pediatrics, University of Dresden, Dresden, Germany
7. Department of Epidemiology, University of Ulm, Ulm, Germany