United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "June 1983," PPI Detailed Report (June 1983) : 12-12. https://fraser.stlouisfed.org/title/63/item/21571/toc/175217 , accessed on June 24, 2024.
United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "June 1983," PPI Detailed Report (June 1983) : 12-12. https://fraser.stlouisfed.org/title/63/item/21571/toc/175217 , accessed on June 24, 2024.