Paco Underhill (2009). “Why We Buy: The Science of Shopping--Updated and Revised for the Internet, the Global Consumer, and Beyond”, p.24, Simon and Schuster
Letter to his brother Robertson of the Financial Reform Association at Liverpool in 1859. "Gladstone as Financier and Economist" by F. W. Hirst, p. 241, 1931.
United States. President (1981-1989 : Reagan), United States. President (1981-1989 : Reagan)., Ronald Reagan, United States. Office of the Federal Register (1982). “Ronald Reagan”