1. Cole, N. L. (2019). Understanding major demographic shifts in the U.S. Retrieved from
https://www.thoughtco.com/demographic-shifts-of-age-and-race-in-the-us-3026679
2. Engel, G. (1977). The need for a new medical model: A challenge for biomedicine. Science, 196, 129–135.
3. Omran, A. R. (1971). The epidemiologic transition: A theory of the epidemiology of population change. Milbank Memorial Fund Quarterly, 49, 515ff.
4. Parsons, T. (1951). The social system. New York: Free Press.
5. Starr, P. C. (1982). The social transformation of American medicine: The rise of a sovereign profession and the making of a vast industry. New York: Basic Books.