United States. Bureau of Economic Analysis. "U.S. International Trade in Goods and Services March 2013, BEA 13-20, CB 13-66, FT-900 (13-03)," Bureau of Economic Analysis (BEA) News Releases (May 2, 2013). https://fraser.stlouisfed.org/title/6148/item/601544, accessed on March 19, 2025.