1. Research Committee of Greek Association of General Practitioners, Thessaloniki, Greece
2. Department of Social Medicine, Faculty of Medicine, University of Crete, Crete, Greece
3. School of Social Sciences, Hellenic Open University, Patra, Greece
4. Health Centre of N. Makri, Athens, Greece
5. Department of Internal Medicine, Faculty of Medicine, School of Health Sciences, University of Ioannina, Ioannina, Greece
6. Health Center of Goura, Korinthia, Greece
7. Health Centre of Evosmos, Thessaloniki, Greece
8. Department of Hygiene, Social-Preventive Medicine and Medical Statistics, School of Medicine, Aristotle University of Thessaloniki, Thessaloniki, Greece