Magombedze, G., Z. Mukandavire, C. Chiyaka, and G. Musuka. “Optimal Control of a sex‐structured HIV/AIDS Model With Condom Use”. Mathematical Modelling and Analysis, vol. 14, no. 4, Dec. 2009, pp. 483-94, doi:10.3846/1392-6292.2009.14.483-494.