United States. Bureau of Economic Analysis. "Gross Domestic Product: First Quarter 2009 (Advance) : Technical Note, BEA 09-17,"
Bureau of Economic Analysis (BEA) News Releases
(April 29, 2009).
https://fraser.stlouisfed.org/title/6148/item/600667/content/pdf/bea_newsreleases_20090429_technical-note, accessed on July 13, 2025.