1. Section for Preventive Medicine and Epidemiology, Department of Community Medicine, Institute of Health and Society, University of Oslo, Oslo, Norway.
2. Himalayan Health and Environmental Services Solukhumbu, Kathmandu, Nepal.
3. Tibet University Medical College, Lhasa, China.
4. National Institute of Public Health, Oslo, Norway.
5. Epidemiology Unit, Prince of Songkla University, Hat Yai, Thailand.