1. National health expenditures, 1991;Letsch;Health Care Financing Review,1993
2. US health expenditure performance: An international comparison and update;Schieber;Health Care Financing Review,1992
3. Health Maintenance Organizations: Dimensions of Performance;Luft,1981
4. The history and spirit of the HMO movement: The early years;Nelson;HMO Practice,1987
5. Public Health Service Act, title 13 (Health Maintenance Act of 1973),1976