1. School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran,
2. School of Medicine, Tehran University of Medical Sciences, Tehran,
3. Dental Materials and Restorative Dentistry, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran;
4. Servizio di Epidemiologia Clinica delle Malattie Respiratorie, Istituti Clinici Scientifici Maugeri Istituto di Ricovero e Cura a Carattere Scientifico, Tradate, Italy;
5. Public Health Consulting Group, Lugano, Switzerland;
6. Unità di Epidemiologia Clinica e Statistica Medica, Dipartimento di Scienze Mediche Chirurgiche e Sperimentali, Università degli Studi di Sassari, Sassari, Italy;
7. Department of Microbiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran