United States. Bureau of Economic Analysis. "U.S. International Trade in Goods and Services: March 2018 : Highlights: March 2018 Trade Gap is $49.0 Billion, BEA 18-21, CB 18-69,"
Bureau of Economic Analysis (BEA) News Releases
(May 3, 2018).
https://fraser.stlouisfed.org/title/6148/item/602628/content/pdf/bea_newsreleases_20180503_release-highlights-monthly, accessed on June 13, 2025.