United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "March 1982," PPI Detailed Report (March 1982) : 15-15. https://fraser.stlouisfed.org/title/63/item/21556/toc/57582 , accessed on April 24, 2024.
United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "March 1982," PPI Detailed Report (March 1982) : 15-15. https://fraser.stlouisfed.org/title/63/item/21556/toc/57582 , accessed on April 24, 2024.