21 February 2013 | Publisher: United States Congressional Research Service | Document type: Research, Background and Discussion Papers
19 February 2013 | Publisher: United States Congressional Research Service | Document type: Research, Background and Discussion Papers
23 December 2010 | Publisher: United States Congressional Research Service | Document type: Research, Background and Discussion Papers
6 December 2010 | Publisher: United States Congressional Research Service | Document type: Research, Background and Discussion Papers