United States. Bureau of Economic Analysis. "Gross Domestic Product: Fourth Quarter 2011 and Annual 2011 (Second Estimate) : Technical Note, BEA 12-05," Bureau of Economic Analysis (BEA) News Releases (February 29, 2012). https://fraser.stlouisfed.org/title/6148/item/601319/content/pdf/bea_newsreleases_20120229_technical-note, accessed on March 25, 2025.