United States. Bureau of Economic Analysis. "U.S. International Trade in Goods and Services: April 2006, CB 06-86, BEA 06-25, FT-900 (06-04)," Bureau of Economic Analysis (BEA) News Releases (June 9, 2006). https://fraser.stlouisfed.org/title/6148/item/598036, accessed on June 17, 2025.