United States. Bureau of Economic Analysis. "Gross Domestic Product: First Quarter 2013 (Advance Estimate) : Historical Comparison, BEA 13-18,"
Bureau of Economic Analysis (BEA) News Releases
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https://fraser.stlouisfed.org/title/6148/item/601542/content/pdf/bea_newsreleases_20130426_historical-comparisons, accessed on July 9, 2025.