1. Porta M. A dictionary of epidemiology. 6th ed. New York: Oxford University Press; 2014.
2. American Dental Association. Specialty definitions. https://www.ada.org/en/ncrdscb/dental-specialties/specialty-definitions. Adopted Mar 2018.
3. Centers for Disease Control and Prevention. Ten great public health achievements. United States, 1900–1999. https://www.cdc.gov/mmwr/preview/mmwrhtml/00056796.htm.
4. Gordis L. Epidemiology. 5th ed. Philadelphia, PA: Elsevier Saunders; 2014.
5. Rothman KJ, Greenland S. Types of epidemiological studies. In: Rothman KJ, Greenland S, editors. Modern epidemiology. 2nd ed. Philadelphia, PA: Lippincott-Raven; 1998.