United States. Bureau of Economic Analysis. "U.S. International Trade in Goods and Services, July 2021 : Historical Comparisons, BEA 21-42, CB 21-138," Bureau of Economic Analysis (BEA) News Releases (September 2, 2021). https://fraser.stlouisfed.org/title/6148/item/606280/content/pdf/bea_newsreleases_20210902_historical, accessed on March 23, 2025.