United States. Bureau of Labor Statistics. "Manufacturing Sector - Appendix - Quarterly Data," in United States. Bureau of Labor Statistics. "First Quarter 2001 [Preliminary]," Productivity and Costs (May 8, 2001) : 13-13. https://fraser.stlouisfed.org/title/131/item/55777/toc/445806 , accessed on April 25, 2024.