Al-Zubaidi, Usama I. M., and Muhammad-Baqir M-R. Fakhrildin. “Influence of Different Concentrations of Sildenafil Citrate on Histological Parameters of Mice Epididymis”. Journal of Biotechnology Research Center (JOBRC), vol. 5, no. 2, June 2011, pp. 55-60, doi:10.24126/jobrc.2011.5.2.165.