APA (7th ed.) Citation

U.S. Census Bureau. (2000). Population of the United States, April 1, 2000. U.S. Census Bureau.

Chicago Style (17th ed.) Citation

U.S. Census Bureau. Population of the United States, April 1, 2000. [Washington, D.C.]: U.S. Census Bureau, 2000.

MLA (9th ed.) Citation

U.S. Census Bureau. Population of the United States, April 1, 2000. U.S. Census Bureau, 2000.