United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "February 1985," PPI Detailed Report (February 1985) : 13-13. https://fraser.stlouisfed.org/title/63/item/21591/toc/321500 , accessed on March 28, 2024.
United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "February 1985," PPI Detailed Report (February 1985) : 13-13. https://fraser.stlouisfed.org/title/63/item/21591/toc/321500 , accessed on March 28, 2024.