HIV-1 progression in hepatitis-C-infected drug users [3] (multiple letters) - Cainelli F; Longhi MS; Concia E; Vento S; Soriano V; Martín JC; González-Lahoz J; Macías J; Pineda JA; Leal M; Lissen E; Greub G; et al. (Lancet, 2001)