United States. Bureau of Labor Statistics. "Durable Manufacturing Sector - Appendix - Annual Data," in United States. Bureau of Labor Statistics. "Second Quarter 1989 [Preliminary]," Productivity and Costs (August 3, 1989) : 23-23. https://fraser.stlouisfed.org/title/131/item/55907/toc/457647 , accessed on April 19, 2024.