1. 1. Rizzetto M , Ponzetto A , Forzani I. Hepatitis delta virus as a global health problem. Vaccine 1990; 8: S10-4.
2. 2. Rizzetto M , Hadziyannis SJ , Hansson BG , Toukan A , Gust I. Hepatitis delta virus infection in the world: epidemiological patterns and clinical expression. Gastroenterol Int 1992; 5: 18-32.
3. 4. Smedile A , Lavarini C , Farci P , et al. Epidemiologic patterns of infection with the hepatitis B virus-associated delta agent in Italy. Am J Epidemiol 1983; 117: 223-9.
4. 5. Sagnelli E , Stroffolini T , Ascione A , et al. The epidemiology of hepatitis delta infection in Italy. J Hepatol 1992; 15: 211-5.