1. The National Board of Health and Welfare. The Swedish Hospital Discharge Registry.
2. The National Board of Health and Welfare. The Cause of Death Register.
3. Population statistics.
4. The National Board of Health and Welfare. The Swedish Classification of Surgical Procedures 6th edition; 1993.
5. The National Board of Health and Welfare. The Swedish Classification of Surgical Procedures 1997; 2004.