Aydin E, Hizal E, Onay O, Ozgen B, Turhan B, Zaimoglu M, Peskircioglu L, Budakoglu II. A Double-blind, Placebo-controlled, Randomized Clinical Study of the Effects of Vardenafil on Human Nasal Patency. American Journal of Rhinology. 2008 May;22(3):276–9. doi: 10.2500/ajr.2008.22.3169.