United States. Bureau of Labor Statistics. "Contents," in United States. Bureau of Labor Statistics. "April 1988," PPI Detailed Report (April 1988) : 3-3. https://fraser.stlouisfed.org/title/63/item/21629/toc/416864 , accessed on March 28, 2024.
United States. Bureau of Labor Statistics. "Contents," in United States. Bureau of Labor Statistics. "April 1988," PPI Detailed Report (April 1988) : 3-3. https://fraser.stlouisfed.org/title/63/item/21629/toc/416864 , accessed on March 28, 2024.