Wyanov, U. and Gandakusuma, I. 2023. Optimal Portfolio Formation Analysis vs. Single Index Model: 2018–2019 Before Crisis and 2020–21 During Crisis. Jurnal Manajemen Bisnis. 10, 2 (Sep. 2023), 588–596. DOI:https://doi.org/10.33096/jmb.v10i2.576.