1. Canada: Statistics Canada. Therapeutic Abortions/Avortements Therapeutics'. Ottawa. Published annually.
2. Tietze, C. ‘Induced Abortion’. The Population Council, New York. Published every other year. Fourth (1981) edition now in preparation.
3. United Kingdom: Office of Population Censuses and Surveys. Abortion Statistics'. HMSO, London. Published annually.
4. United States: Center for Disease Control. Abortion Surveillance'. Atlanta, Georgia. Published annually.