Tài liệu tham khảo WikiPedia: Vardenafil http://www.medscape.com/viewarticle/549253_6 http://www.fda.gov/NewsEvents/Newsroom/PressAnnoun... //www.ncbi.nlm.nih.gov/pubmed/19474796 //dx.doi.org/10.1038%2Fijir.2009.21
