Valiquette, L., F. Montorsi, and S. Auerbach. “Vardenafil Demonstrates First-Dose Success and Reliability of Penetration and Maintenance of Erection in Men With Erectile Dysfunction — RELY-II”. Canadian Urological Association Journal, vol. 2, no. 3, Apr. 2013, pp. 187-95, doi:10.5489/cuaj.590.