High frequency of the GWG (Prp Trp) envelope variant of HIV-1 in southeast Brazil - Covas, Dimas Tadeu; Bíscaro, Taísa; Kashima, Simone; Duarte, Geraldo; Machado, Alcyone Artioli (Journal of Acquired Immune Deficiency Syndromes and Human Retrovirology, 1998)