United States. Bureau of Labor Statistics. "Durable Manufacturing Sector - Appendix - Quarterly Data," in United States. Bureau of Labor Statistics. "Second Quarter 1999 [Preliminary]," Productivity and Costs (August 5, 1999) : 15-15. https://fraser.stlouisfed.org/title/131/item/55966/toc/440570 , accessed on May 2, 2024.