Gjersing, L., H. Waal, J. Røislien, M. Gossop, and T. Clausen. “Variations in Treatment Organisation, Practices and Outcomes Within the Norwegian Opioid Maintenance Treatment Programme”. Norsk Epidemiologi, vol. 21, no. 1, Dec. 2011, doi:10.5324/nje.v21i1.1434.