Yábar V, C., Salvatierra F, J. and Quijano, E. (2007) “Envelope genetic variability of HIV-1 infecting human groups with differents risk sexual behaviour to adquire HIV-STD”, Revista Peruana de Medicina Experimental y Salud Pública, 24(3). doi:10.17843/rpmesp.2007.243.1108.