United States. Bureau of Labor Statistics. "Durable Manufacturing Sector - Appendix - Quarterly Data," in United States. Bureau of Labor Statistics. "Second Quarter 2001 [Preliminary]," Productivity and Costs (August 7, 2001) : 15-15. https://fraser.stlouisfed.org/title/131/item/55964/toc/445978 , accessed on May 2, 2024.