United States. Bureau of Labor Statistics. "Manufacturing Sector," in United States. Bureau of Labor Statistics. "Private Business, Nonfarm Business, and Manufacturing Sectors : Second Quarter 1981," Productivity and Costs (July 30, 1981) : 9-9. https://fraser.stlouisfed.org/title/131/item/55906/toc/437975 , accessed on May 2, 2024.