Robert Fortune (1847). “Three Years' Wanderings in the Northern Provinces of China: Including a Visit to the Tea, Silk, and Cotton Countries; with an Account of the Agriculture and Horticulture of the Chinese, New Plants, Etc”, p.141
John George Nicolay (2008). “A Short Life of Abraham Lincoln: Condensed from Nicolay & Hay's Abraham Lincoln: a History: Easyread Large Edition”, p.40, ReadHowYouWant.com
United States. President (1981-1989 : Reagan), United States. President (1981-1989 : Reagan)., Ronald Reagan, United States. Office of the Federal Register (1983). “Ronald Reagan”