United States. Bureau of Labor Statistics. "Manufacturing Sector - Appendix - Quarterly Data," in United States. Bureau of Labor Statistics. "Third Quarter 1999 [Revised]," Productivity and Costs (December 7, 1999) : 13-14. https://fraser.stlouisfed.org/title/131/item/55939/toc/442040 , accessed on April 19, 2024.