Cook, Colleen W. (16 October 2007). Mexico's Drug Cartels(PDF). CRS Report for Congress. Congressional Research Service. p. 7. สืบค้นเมื่อ 10 May 2016.
Seelke, Clare Ribando (29 January 2013). Mexico and the 112th Congress(PDF). Congressional Research Service. pp. 2, 13, 14. สืบค้นเมื่อ 10 May 2016.