↑ Shafritz, Jay; Ott, J. Steven. "Classical Organization Theory". In Shafritz, Jay; Ott, J. Steven. Classics of Organization Theory (5 ed.). Orlando: Harcourt. p. 33. ISBN0-15-506869-5.
↑ Gulick, Luther (1937). "Notes on the Theory of Organization". In Gulick, Luther; Urwick, Lyndall. Papers on the Science of Administration. New York: Institute of Public Administration. p. 13.