Effects of voucher-based intervention on abstinence and retention in an outpatient treatment for cocaine addiction: a randomized controlled trial
Experimental and Clinical Psychopharmacology (2009) - Comment
pubmed: 19586227  doi: 10.1037/a0015963  issn: 1064-1297  issn: 1936-2293 

Olaya Garcia-Rodriguez, Roberto Secades-Villa, Stephen T. Higgins, Jose R. Fernandez-Hermida, Jose L. Carballo, Jose M. Errasti Perez, Susana Al-halabi Diaz