United States. Bureau of Economic Analysis. "U.S. International Trade in Goods and Services, February 2011, BEA 11-15, CB 11-66, FT-900 (11-02)," Bureau of Economic Analysis (BEA) News Releases (April 12, 2011). https://fraser.stlouisfed.org/title/6148/item/604074, accessed on March 27, 2025.