United States. Bureau of Labor Statistics. "Durable Manufacturing Sector - Appendix - Quarterly Data," in United States. Bureau of Labor Statistics. "Second Quarter 1988 [Preliminary]," Productivity and Costs (August 4, 1988) : 16-16. https://fraser.stlouisfed.org/title/131/item/55807/toc/454939 , accessed on May 16, 2024.