Cook RL, McGinnis KA, Samet JH, Fiellin DA, Rodriguez-Barradas MC, Rodriquez-Barradas MC, Kraemer KL, Gibert CL, Braithwaite RS, Goulet JL, Mattocks K, Crystal S, Gordon AJ, Oursler KK, Justice AC. Erectile dysfunction drug receipt, risky sexual behavior and sexually transmitted diseases in HIV-infected and HIV-uninfected men. J Gen Intern Med. 2010 Feb; 25(2):115-21.