- United States. Dept. of Commerce. American FactFinder. US Census Bureau. n.d. Web. 1 Apr. 2014.
- United States. Environmental Protection Agency. EPA. Washington, DC: Environmental Protection Agency. 21 Mar. 2014 Web. 2 Apr. 2014.
- United States. General Services Administration. Office of Citizen Services and Innovative Technologies. USA.gov: 50 States and the District of Columbia. Washington, DC: General Services Administration. 4 Mar. 2014 Web. 2 Apr. 2014.
- United States. Government Printing Office. FD SYS: Federal Digital System. Washington, DC: US Government Printing Office, n.d. Web. 2 Apr. 2014.