United States. Bureau of Economic Analysis. "Gross Domestic Product by Industry: First Quarter 2019 : Full Release, BEA 19-33," Bureau of Economic Analysis (BEA) News Releases (July 19, 2019). https://fraser.stlouisfed.org/title/6148/item/602806/content/pdf/bea_newsreleases_20190719, accessed on March 21, 2025.