United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "June 1984," PPI Detailed Report (June 1984) : 13-13. https://fraser.stlouisfed.org/title/63/item/21583/toc/427362 , accessed on April 25, 2024.
United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "June 1984," PPI Detailed Report (June 1984) : 13-13. https://fraser.stlouisfed.org/title/63/item/21583/toc/427362 , accessed on April 25, 2024.