United States. Bureau of Economic Analysis. "Gross Domestic Product: Fourth Quarter and Annual 2013 (Advance Estimate) : Historical Comparison, BEA 14-03,"
Bureau of Economic Analysis (BEA) News Releases
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https://fraser.stlouisfed.org/title/6148/item/602083/content/pdf/bea_newsreleases_20140130_historical-comparisons, accessed on July 8, 2025.