Ningsih, Cahaya, and Pipit Yunianingsih. 2026. “Optimal Portfolio Analysis Using the Markowitz Model and Single Index Model on Jakarta Islamic Index (JII) Stocks: Historical Data 2022–2025”. Indonesian Interdisciplinary Journal of Sharia Economics (IIJSE) 9 (1), 9810-31. https://doi.org/10.31538/iijse.v9i1.9567.