Prevalence of the HCV genotypes in two periods 1990-1997 and 1999-2007 in a cohort of patients in São Paulo, Brazil - Cavalheiro, Norma P.; Barone, Antonio Alci; Melo, Carlos E.; Tengan, Fatima M.; Araújo, Evaldo S. A. de (International Symposium on Hepatitis C Virus & Related Viruses, 2008)