Siahaan, Rekolina, and Holmes Rajagukguk. 2021. “Students Barriers in Online Learning of Covid 19 Pandemic for Fifth Grade in English Language Study Program of Sisingamangaraja XII University Tapanuli”. Jurnal Mantik 5 (3):1944-47. https://iocscience.org/ejournal/index.php/mantik/article/view/1805.