United States. Bureau of Labor Statistics. "Durable Manufacturing Sector - Appendix - Quarterly Data," in United States. Bureau of Labor Statistics. "Second Quarter 1997 [Preliminary]," Productivity and Costs (August 12, 1997) : 16-16. https://fraser.stlouisfed.org/title/131/item/55927/toc/433741 , accessed on May 3, 2024.