Viagra's licence and the internet.
D003195:Computer Communication Networks; D000075202:Contraindications; D017277:Drug Approval; D004791:Enzyme Inhibitors / Q000600:supply & distribution*; D007172:Erectile Dysfunction / Q000188:drug therapy; D006801:Humans; D008297:Male; D010879:Piperazines / Q000600:supply & distribution*; D011687:Purines; D000068677:Sildenafil Citrate; D013450:Sulfones; D006113:United Kingdom; D014481:United States
D004791:Enzyme Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D000068677:Sildenafil Citrate