1. Respiratory Medicine Department, University of Ioannina, Ioannina, Greece
2. 2nd Respiratory Medicine Department, National and Kapodistrian University of Athens, Athens, Greece
3. Respiratory Medicine Department, Corfu General Hospital, Corfu, Greece
4. 5th Respiratory Medicine Department, Sotiria Chest Hospital, Athens, Greece
5. 1st Respiratory Medicine Department, National and Kapodistrian University of Athens, Athens, Greece