1. University of Oslo,; Norvegian Centre for Addiction Research; Kirkeveien 166 Oslo Norway 0407
2. Health Services; Norvegian Knowlege Centre; PO Box 7004, St Olavsplass Oslo Norway 0130
3. University of Oslo; Unit of Addiction Medicine; Kirkeveien 166 Oslo Norway 0407
4. Norwegian Health Services Research Centre; Postbox 7004 St. Olavs plass Oslo Norway 0031