Persistence in the Methadone Maintenance Program and Its Relationship with the Medication Regimen Complexity Index in Opioid-Dependent Patients oleh Elena Alba Álvaro-Alonso, María del Carmen Gómez-Álvarez, Beatriz Segovia-Tapiador, María Isabel Del-Pino-Illaconza, Jorge Valencia, Pablo Ryan, Antonio Aguilar-Ros, Ismael Escobar-Rodríguez