"Panama Canal Zone." YourDictionary, n.d. Web. 19 September 2018. <http://www.yourdictionary.com/panama-canal-zone>.
Panama Canal Zone. (n.d.). Retrieved September 19th, 2018, from http://www.yourdictionary.com/panama-canal-zone
(history) The territory within Panama, stretching along the course of the Panama Canal but excluding the sea port cities Panama City and Colon under the 18 November 1903 lease treaty until the return of state control on 30 September 1979.
English Wiktionary. Available under CC-BY-SA license.