For the text of Wilson's message, see Edgar Eugene Robinson and Victor J. West, The Foreign Policy of Woodrow Wilson, 1913–1917 (NY: Macmillan, 1918), 207–9, available online, accessed February 8, 2011
Ira E. Bennett, History of the Panama Canal, Its Construction and Builders (Washington, DC: Historical Publishing, 1915), 241–2, available online, accessed February 8, 2011
jstor.org
W. S. Coker, "The Panama Canal Tolls Controversy: A Different Perspective" Journal of American History (1968), 55(3), 555-564. online