1. Grundy F, Mackintosh JM. The Teaching of Hygiene and Public Health in Europe. Geneva: World Health Organization, 1957: 27.
2. Ibid, p. 2.
3. Sand R. The Advance of Social Medicine. London: Staples Press, 1952: 181.
4. Garrison FH. An Introduction to the History of Medicine. 4th Ed. Philadelphia: Saunders, 1929: 717.
5. Osler W. The Principles and Practice of Medicine. 4th Ed. New York: Appleton, 1901.