United States. Bureau of Economic Analysis. "Gross Domestic Product: Fourth Quarter and Annual 2013 (Second Estimate) : Historical Comparison, BEA 14-06," Bureau of Economic Analysis (BEA) News Releases (February 28, 2014). https://fraser.stlouisfed.org/title/6148/item/602086/content/pdf/bea_newsreleases_20140228_historical-comparisons, accessed on March 21, 2025.