United States. Bureau of Labor Statistics. "Durable Manufacturing Sector - Appendix - Quarterly Data," in United States. Bureau of Labor Statistics. "Second Quarter 1989 [Preliminary]," Productivity and Costs (August 3, 1989) : 17-17. https://fraser.stlouisfed.org/title/131/item/55907/toc/457635 , accessed on April 18, 2024.