United States. Bureau of Labor Statistics. "Manufacturing Sector - Appendix - Quarterly Data," in United States. Bureau of Labor Statistics. "Fourth-Quarter and Annual Averages, 1993," Productivity and Costs (March 8, 1994) : 15-15. https://fraser.stlouisfed.org/title/131/item/55835/toc/477750 , accessed on March 28, 2024.