Wang, Haoxiong. “Portfolio Risk Analysis and Optimization of U.S. Technology Stocks: Evidence from Apple, Microsoft, NVIDIA, and Amazon Benchmarked Against the NASDAQ Composite Index”. Finance & Economics 4, no. 5 (October 1, 2026): 11102. Accessed October 19, 2026. https://fe.deanfrancis.press/article/view/1193.