title: Lessons from the viagra study: methodological challenges in recruitment of older and minority heterosexual men for research on sexual practices and risk behaviors.
authors.forename: Sande Gracia
authors.initials: SG
authors.lastname: Jones
authors.forename: Carol A
authors.initials: CA
authors.lastname: Pat Patsdaughter
authors.forename: Vicente Manuel
authors.initials: VM
authors.lastname: Martinez Cardenas
mesh_terms: D000368:Aged; D015658:HIV Infections / Q000453:epidemiology / Q000635:transmission; D006801:Humans; D008297:Male; D008875:Middle Aged; D008913:Minority Groups; D058986:Phosphodiesterase 5 Inhibitors / Q000008:administration & dosage*; D010879:Piperazines / Q000008:administration & dosage*; D011687:Purines / Q000008:administration & dosage; D012309:Risk-Taking; D012725:Sexual Behavior; D000068677:Sildenafil Citrate; D013450:Sulfones / Q000008:administration & dosage*
chemical_list: D058986:Phosphodiesterase 5 Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D000068677:Sildenafil Citrate