*[[United States Department of the Treasury]], Bureau of the Public Debt. [http://www.treasurydirect.gov/govt/reports/pd/histdebt/histdebt.htm "Government – Historical Debt Outstanding – Annual"]. TreasuryDirect. Retrieved January 16, 2011.</ref> | *[[United States Department of the Treasury]], Bureau of the Public Debt. [http://www.treasurydirect.gov/govt/reports/pd/histdebt/histdebt.htm "Government – Historical Debt Outstanding – Annual"]. TreasuryDirect. Retrieved January 16, 2011.</ref> |