Headrick. When Information Came of Age. P. 190.

Lewis Mumford. Technics and Civilization. London, 1934. P. 109–110.

Peter S. Onuf. Statehood and the Union: A History of the Northwest Ordinance. Bloomington, IN, 1987. P. 1, 33; R. A. Billington. Westward Expansion: A History of the American Frontier. 3rd ed. New York, 1967. P. 210. См. также: Andrew R. L. Cayton. The Frontier Republic: Ideology and Politics in the Ohio Country, 1780–1825. Kent, Ohio, 1986. P. 7–9.