United States. Bureau of Economic Analysis. "Gross Domestic Product (Third Estimate), Corporate Profits (Revised Estimate), and GDP by Industry, Second Quarter 2021 : Technical Note, BEA 21-47," Bureau of Economic Analysis (BEA) News Releases (September 30, 2021). https://fraser.stlouisfed.org/title/6148/item/607753/content/pdf/bea_newsreleases_20210930_technote, accessed on March 26, 2025.