Farag, R. S., El Nawawy, M. A., Fathy, W. M. and Atiaa, H. (2013) “Effect of oral injection of tramadol, sildenafil and combined of tramadol and sildenafil on serum testosterone level for Wistar breed male rats”, INTERNATIONAL JOURNAL OF COMPUTERS & TECHNOLOGY, 11(9), pp. 2959–2966. doi: 10.24297/ijct.v11i9.3411.