Purnomo, Dwi Tjahjo. “APAKAH SAHAM FARMASI DI BURSA EFEK INDONESIA MENGIKUTI HIPOTESIS RANDOM WALK SAAT PANDEMI COVID-19?”. Jurnal Riset Ekonomi Dan Bisnis, vol. 14, no. 1, Apr. 2021, pp. 18-28, https://doi.org/10.26623/jreb.v14i1.3170.