SIAHAAN, R.; RAJAGUKGUK , H. . . Students Barriers in Online Learning of Covid 19 Pandemic for Fifth Grade in English Language Study Program of Sisingamangaraja XII University Tapanuli. Jurnal Mantik, [S. l.], v. 5, n. 3, p. 1944-1947, 2021. Disponível em: https://iocscience.org/ejournal/index.php/mantik/article/view/1805. Acesso em: 21 apr. 2026.