Juliana, Nita, and Dr. Gustian Djuanda , trans. 2023. “Analysis of Formation of Optimal Portfolio Single Index Model (Study of Cigarette Sub-Sector Manufacturing Companies Period 2020-2021)”. West Science Journal Economic and Entrepreneurship 1 (01): 37-41. https://wsj.westsciences.com/index.php/wsee/article/view/26.