United States. Bureau of Economic Analysis. "Gross Domestic Product: Fourth Quarter 2007 (Preliminary) : Technical Note, BEA 08-06,"
Bureau of Economic Analysis (BEA) News Releases
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https://fraser.stlouisfed.org/title/6148/item/600439/content/pdf/bea_newsreleases_20080228_technical-note, accessed on June 21, 2025.