United States. Bureau of Labor Statistics. "Recalculated Producer Price Indexes for SIC 7372, Prepackaged Software," in United States. Bureau of Labor Statistics. "May 2001," PPI Detailed Report (May 2001) : 10-10. https://fraser.stlouisfed.org/title/63/item/21787/toc/307842 , accessed on May 4, 2024.