United States. Bureau of Labor Statistics. "Footnotes," in United States. Bureau of Labor Statistics. "Private Business, Nonfarm Business, and Manufacturing Sectors : Third Quarter 1977," Productivity and Costs (October 27, 1977) : 14-14. https://fraser.stlouisfed.org/title/131/item/55877/toc/494921 , accessed on May 2, 2024.