United States. Bureau of Labor Statistics. "Durable 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) : 21-21. https://fraser.stlouisfed.org/title/131/item/55906/toc/437973 , accessed on May 1, 2024.