United States. Bureau of Economic Analysis. "U.S. International Trade in Goods and Services, February 2021 : Historical Comparisons, BEA 21-17, CB 21-50," Bureau of Economic Analysis (BEA) News Releases (April 7, 2021). https://fraser.stlouisfed.org/title/6148/item/601759/content/pdf/bea_newsreleases_20210407_historical, accessed on March 21, 2025.