title: Reducing drug use among methadone maintenance clients: contingent reinforcement for morphine-free urines.
mesh_terms: D000328:Adult; D006556:Heroin Dependence / Q000534:rehabilitation*; D006801:Humans; D008297:Male; D008691:Methadone / Q000627:therapeutic use*; D009020:Morphine / Q000652:urine*; D012054:Reinforcement, Psychology; D019966:Substance-Related Disorders / Q000652:urine
chemical_list: D009020:Morphine; D008691:Methadone