Kristianto, N., and D. Delvia. “LEVELS OF ONLINE LEARNING EFFECTIVENESS IN THE TIME OF THE COVID-19 PANDEMIC USING DIFFERENT APPLICATIONS LEARNING BY STUDENT’S PERCEPTION”. Epsilon: Jurnal Pendidikan Matematika, vol. 3, no. 1, Apr. 2022, https://jurnal.stkippgribl.ac.id/index.php/epsilon/article/view/583.