United States. Bureau of Economic Analysis. "Gross Domestic Product: First Quarter 2015 (Advance Estimate) : Technical Note, BEA 15-18,"
Bureau of Economic Analysis (BEA) News Releases
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https://fraser.stlouisfed.org/title/6148/item/602236/content/pdf/bea_newsreleases_20150429_technical-note, accessed on June 15, 2025.