United States. Bureau of Economic Analysis. "U.S. International Investment Position, Second Quarter 2021 : Full Release, BEA 21-46," Bureau of Economic Analysis (BEA) News Releases (September 28, 2021). https://fraser.stlouisfed.org/title/6148/item/607752/content/pdf/bea_newsreleases_20210928, accessed on March 17, 2025.