Blanchard, Christopher M.; Humud, Carla E. (2 February 2017). "The Islamic State and U.S. Policy"(PDF). Congressional Research Service. Archived(PDF) from the original on 1 January 2019. Retrieved 30 August 2018.
Blanchard, Christopher M.; Humud, Carla E. (2 February 2017). "The Islamic State and U.S. Policy"(PDF). Congressional Research Service. Archived(PDF) from the original on 1 January 2019. Retrieved 30 August 2018.