United States. Bureau of Economic Analysis. "U.S. International Trade in Goods and Services: July 2013, BEA 13-40, CB 13-148, FT-900 (13-07),"
Bureau of Economic Analysis (BEA) News Releases
(September 4, 2013).
https://fraser.stlouisfed.org/title/6148/item/601563, accessed on March 15, 2025.