1. Department of Pharmacoepidemiology; Norwegian Institute of Public Health; Oslo Norway
2. Centre of Public Health Sciences; Faculty of Medicine; University of Iceland Reykjavik; Reykjavik Iceland
3. Research Department; The Social Insurance Institution; Helsinki Finland
4. Centre for Pharmacoepidemiology; Department of Medicine; Solna, Karolinska Institutet; Stockholm Sweden
5. Clinical Pharmacology; Department of Public Health; University of Southern Denmark; Funen Denmark