Meliala, Fitria Ulina, and Subiakto Sukarno. “Optimal Investment Portfolio Analysis Using The Markowitz Model For Stock In Each Sector In The Indonesia Stock Market During Covid 19 (2020-2021)”. Journal Research of Social Science, Economics, and Management 2, no. 8 (March 27, 2023): 1884 –. Accessed October 5, 2024. https://jrssem.publikasiindonesia.id/index.php/jrssem/article/view/399.