Husni, R.A. et al. 2022. Optimal Portfolio Comparison Based on Markowitz and Single Index Model Using IDX BUMN20 Stocks during Covid-19. Indikator: Jurnal Ilmiah Manajemen dan Bisnis. 6, 3 (Aug. 2022), 94–104. DOI:https://doi.org/10.22441/indikator.v6i3.15305.