United States. Bureau of Labor Statistics. "Durable Manufacturing Sector - Appendix - Quarterly Data," in United States. Bureau of Labor Statistics. "Preliminary Fourth-Quarter Measures and Annual Averages, 1998," Productivity and Costs (February 9, 1999) : 16-16. https://fraser.stlouisfed.org/title/131/item/55757/toc/437947 , accessed on April 25, 2024.