1. Department of Pharmacoepidemiology; Norwegian Institute of Public Health; Oslo Norway
2. Centre for Pharmacoepidemiology; Karolinska Institutet; Stockholm Sweden
3. Research Unit for General Practice; University of Southern Denmark; Odense Denmark
4. Department of Clinical Epidemiology, Institute of Clinical Medicine; Aarhus University Hospital; Aarhus Denmark
5. Centre of Public Health Sciences, Faculty of Medicine; University of Iceland; Reykjavik Iceland