Abdel Aziz, M. T., T. Mostafa, H. Atta, L. Rashed, S. A. Marzouk, E. M. Obaia, D. Sabry, A. A. Hassouna, A. M. El-Shehaby, and A. T. Abdel Aziz,  "Oral phosphodiesterase-5 inhibitors: effect of heme oxygenase inhibition on cGMP signalling in rat cavernous tissue",  Andrologia, vol. 39, no. 2: Wiley Online Library, pp. 66?70, 2007.