United States. Department of Commerce. "U.S. International Trade in Goods and Services, December 2011, BEA 12-04, CB 12-27, FT-900 (11-12),"
United States Department of Commerce News
(February 10, 2012).
https://fraser.stlouisfed.org/title/6148/item/601318, accessed on June 3, 2026.