1. Department of Mental Disorders Norwegian Institute of Public Health Oslo Norway
2. Department of Addictology, First Faculty of Medicine Charles University Prague Czech Republic
3. Institute of Health Information and Statistics of the Czech Republic Prague Czech Republic
4. Norwegian Centre for Addiction Research at the University of Oslo Oslo Norway
5. Department of Chronic Diseases and Ageing Norwegian Institute of Public Health Oslo Norway
6. Department of Global Public Health and Primary Care University of Bergen Bergen Norway
7. National Monitoring Centre for Drugs and Addiction Office of the Government of the Czech Republic Prague Czech Republic