C. Yábar V, J. Salvatierra F, and E. Quijano, “Envelope genetic variability of HIV-1 infecting human groups with differents risk sexual behaviour to adquire HIV-STD”, Rev Peru Med Exp Salud Publica, vol. 24, no. 3, Sep. 2007, doi: 10.17843/rpmesp.2007.243.1108.