1. Faculty of Medicine, University of Buenos Aires, C1121ABGBuenos Aires, Argentina
2. Department of Surgery, University of Pisa, 56126 Pisa, Italy
3. Labs of Epidemiological Methods and Biostatistics, Department of Environmental Medicine and Public Health, University of Padova, Via Loredan 18, 35131 Padova, Italy
4. Faculty of Medicine, University of Padova, 35122 Padova, Italy
5. ENT Department, University of Siena, 53100 Siena, Italy