United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "August 1985," PPI Detailed Report (August 1985) : 14-15. https://fraser.stlouisfed.org/title/63/item/21597/toc/144399 , accessed on April 25, 2024.
United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "August 1985," PPI Detailed Report (August 1985) : 14-15. https://fraser.stlouisfed.org/title/63/item/21597/toc/144399 , accessed on April 25, 2024.