United States. Bureau of Labor Statistics. "Wholesale Trade, Retail Trade, and Food Services and Drinking Places, 2003 : Wholesale Trade, Retail Trade, and Food Services and Drinking Places, 2003, USDL 04-1832,"
Productivity and Costs by Industry
(September 24, 2004).
https://fraser.stlouisfed.org/title/9618/item/703978/content/pdf/prin_20040924, accessed on June 9, 2026.