United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "March 1983," PPI Detailed Report (March 1983) : 12-12. https://fraser.stlouisfed.org/title/63/item/21568/toc/427618 , accessed on April 23, 2024.
United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "March 1983," PPI Detailed Report (March 1983) : 12-12. https://fraser.stlouisfed.org/title/63/item/21568/toc/427618 , accessed on April 23, 2024.