United States. Bureau of Economic Analysis. "U.S. International Trade in Goods and Services, April 2007 : Full Release, BEA 07-25, CB 07-81, FT-900 (07-04)," Bureau of Economic Analysis (BEA) News Releases (June 8, 2007). https://fraser.stlouisfed.org/title/6148/item/598966/content/pdf/bea_newsreleases_20070608a_release, accessed on March 17, 2025.