United States. Bureau of Economic Analysis. "National Income and Product Accounts : Second Quarter 2006 GDP (Advance) | Revised Estimates: 2003 Through First Quarter 2006, BEA 06-33," Bureau of Economic Analysis (BEA) News Releases (July 28, 2006). https://fraser.stlouisfed.org/title/6148/item/598043, accessed on June 24, 2025.