1. Harald R. Lie, Social and Health Administration, Municipality of Aarhus, DK-8100 århus C, Denmark., Correspondence Address: Harald R. Lie, M.D., Ph.D. Foniksvej 2 DK-8270 Hojbjerg Denmark
2. Department of Paediatrics, University Hospital, S-751 85 Uppsala, Sweden
3. Department of Paediatrics, Ullevål University Hospital, N-0450 Oslo 4, Norway
4. Department of Paediatrics, University Hospital, S-221 85 Lund, Sweden
5. The Nordic School of Public Health, S-402 42 Göteborg, Sweden