United States. Bureau of Economic Analysis. "Gross Domestic Product by Industry: Fourth Quarter and Annual 2018 : Highlights: Gross Domestic Product by Industry: Fourth Quarter 2018, BEA 19-16," Bureau of Economic Analysis (BEA) News Releases (April 19, 2019). https://fraser.stlouisfed.org/title/6148/item/602789/content/pdf/bea_newsreleases_20190419_highlights, accessed on March 19, 2025.