United States. Bureau of Economic Analysis. "Private Services-Producing Sector Continued to Lead Growth in 2006 : Full Release : Revised Statistics of Gross Domestic Product by Industry, 2004-2006, BEA 08-02," Bureau of Economic Analysis (BEA) News Releases (January 29, 2008). https://fraser.stlouisfed.org/title/6148/item/600435/content/pdf/bea_newsreleases_20080129, accessed on March 21, 2025.