United States. Bureau of Labor Statistics. "Manufacturing Sector - Appendix - Quarterly Data," in United States. Bureau of Labor Statistics. "Second Quarter 1991 [Preliminary]," Productivity and Costs (August 6, 1991) : 16-16. https://fraser.stlouisfed.org/title/131/item/55815/toc/463204 , accessed on May 2, 2024.