1. Zemun Clinical Hospital Centre, Department of Pulmonology, Belgrade, Serbia
2. University Children’s Hospital, Belgrade, Serbia
3. University Children’s Hospital, Belgrade, Serbia + University of Belgrade, Faculty of Medicine, Belgrade, Serbia
4. Military Medical Academy, Clinic for Lung Disease, Belgrade, Serbia
5. Clinical Centre of Serbia, Clinic for Lung Diseases, Belgrade, Serbia + University of Belgrade, Faculty of Medicine, Belgrade, Serbia
6. Institute of Medical Statistics and Informatics, Belgrade, Serbia + University of Belgrade, Faculty of Medicine, Belgrade, Serbia