United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "August 1982," PPI Detailed Report (August 1982) : 14-14. https://fraser.stlouisfed.org/title/63/item/21561/toc/218017 , accessed on April 25, 2024.
United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "August 1982," PPI Detailed Report (August 1982) : 14-14. https://fraser.stlouisfed.org/title/63/item/21561/toc/218017 , accessed on April 25, 2024.