title: Qualitative methodological issues in drug user research.
authors.forename: Avelardo
authors.initials: A
authors.lastname: Valdez
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Sifaneck
mesh_terms: D006801:Humans; D036301:Qualitative Research; D012107:Research Design; D019966:Substance-Related Disorders; D014481:United States