United States. Bureau of Labor Statistics. "Manufacturing Sector - Appendix - Quarterly Data," in United States. Bureau of Labor Statistics. "Private Business, Nonfarm Business, and Manufacturing Sectors : Second Quarter 1981," Productivity and Costs (July 30, 1981) : 20-20. https://fraser.stlouisfed.org/title/131/item/55906/toc/437959 , accessed on May 1, 2024.