United States. Bureau of Economic Analysis. "U.S. International Investment Position: First Quarter 2018, Year 2017, and Annual Update : Full Release, BEA 18-30," Bureau of Economic Analysis (BEA) News Releases (June 27, 2018). https://fraser.stlouisfed.org/title/6148/item/602638/content/pdf/bea_newsreleases_20180627, accessed on March 27, 2025.