1. Respiratory Medicine Department, University of Ioannina School of Medicine, Ioannina, Greece
2. 2nd Department of Respiratory Medicine, Medical School of National and Kapodistrian, “Attikon” Hospital, University of Athens, Athens, Greece
3. Department of Respiratory Medicine,General Oncologic Hospital “St. Anargyroi”, Athens, Greece
4. Laboratory of Social Medicine, Medical School, Democritus University of Thrace, Alexandroupolis, Greece
5. Department of Respiratory Medicine, Medical School, Democritus University of Thrace, Alexandroupolis, Greece