A Randomized Pilot Trial of Contingency-management Intervention for Patients in during Methadone Maintenance Treatment, Cash vs. Vouchers - PIRNIA, Bijan; SOLEIMANI, Ali; TAHERINAKHOST, Hamid Reza; PIRNIA, Kambiz; MALEKANMEHR, Parastoo; ZAHIRODDIN, Alireza (Iranian Journal of Public Health, 2018)