1. National Centre for Healthcare Research & Pharmacoepidemiology, Milan, Italy
2. Department of Statistics and Quantitative Methods, University of Milano-Bicocca, Milan, Italy
3. Department of Epidemiology, Lazio Regional Health Service, Roma, Italy
4. Authority for Healthcare and Welfare, Emilia Romagna Regional Health Service, Bologna, Italy
5. Epidemiologic Observatory, Lombardy Regional Health Service, Milan, Italy
6. Department of Health Planning, Italian Health Ministry, Rome, Italy
7. Center of Epidemiology and Biostatistics, Polytechnic University of Marche, Ancona, Italy