- Therapeutic Effectiveness and Patient Satisfaction after 6 Months of Treatment with Tadalafil, Sildenafil, and Vardenafil: Results from the Erectile Dysfunction Observational Study (EDOS). Martin-Morales, A., Haro, J.M., Beardsworth, A., Bertsch, J., Kontodimas, S. Eur. Urol. (2007)