REFERENCES
- Statistical Abstract of the United States. Department of Commerce, 1972
- Loewenstein MS, Balows A, Gangarosa EJ: Turista at an international congress in Mexico. Lancet 1:529–531, Mar 10, 1973
- Discussion of current issues concerning the United States smallpox vaccination policy. Newsletter of American College of Preventive Medicine 15:6–7, 1973