United States. Bureau of Labor Statistics. "Productivity and Costs by Industry, 2001 : Productivity and Costs by Industry, 2001, USDL 03-490," Productivity and Costs by Industry (September 22, 2003). https://fraser.stlouisfed.org/title/9618/item/703975/content/pdf/prin_20030922, accessed on June 13, 2026.