United States. Bureau of Labor Statistics. "Nonfinancial Corporations - Appendix - Quarterly Data," in United States. Bureau of Labor Statistics. "Second Quarter 1999 [Preliminary]," Productivity and Costs (August 5, 1999) : 17-17. https://fraser.stlouisfed.org/title/131/item/55966/toc/440561 , accessed on March 29, 2024.