1. O. Blix, and L. Gronbladh(1988 ) AIDS and IV heroin addicts: the preventive effect of methadone maintenance in Sweden, Presented at the Fourth International Conference on AIDS, Stockholm, Sweden.
2. M. Calello, O. Libonatti, M. Boxaca, and M. Weissen-Bacher(1991 ) Increasing risk of heterosexual HIV-1 spreading due to intravenous drug use in Argentina. Presented at the Seventh International Conference on AIDS, Florence, Italy.