United States. Bureau of Labor Statistics. "Mining," in United States. Bureau of Labor Statistics. "July 1982," PPI Detailed Report (July 1982) : 114-114. https://fraser.stlouisfed.org/title/63/item/21560/toc/194317 , accessed on April 18, 2024.
United States. Bureau of Labor Statistics. "Mining," in United States. Bureau of Labor Statistics. "July 1982," PPI Detailed Report (July 1982) : 114-114. https://fraser.stlouisfed.org/title/63/item/21560/toc/194317 , accessed on April 18, 2024.