"Boundary Changes". Geographic Change Notes: Oklahoma. Population Division, United States Census Bureau. May 19, 2006. Archived from the original on February 6, 2006. Retrieved July 13, 2008.
"Boundary Changes". Geographic Change Notes: Oklahoma. Population Division, United States Census Bureau. May 19, 2006. Archived from the original on February 6, 2006. Retrieved July 13, 2008.