Davstad, MA, I., M. Stenbacka, PhD, A. Leifman, MSE, O. Beck, PhD, S. Korkmaz, MD, PhD, and A. Romelsjo, MD, PhD. “Patterns of Illicit Drug Use and Retention in a Methadone Program: A Longitudinal Study”. Journal of Opioid Management, vol. 3, no. 1, Jan. 2007, pp. 27-34, doi:10.5055/jom.2007.0036.