United States. Bureau of Labor Statistics. "Producer Price Indexes by Durability of Product, Not Seasonally Adjusted," in United States. Bureau of Labor Statistics. "April 2008 (Corrected)," PPI Detailed Report (April 2008) : 142-142. https://fraser.stlouisfed.org/title/63/item/21869/toc/370456 , accessed on April 25, 2024.