Ritonga M, Lahmi A, Saputra R, Mursal, Nofrizaldi N. Online learning during the Covid-19 pandemic period: Studies on the social presence and affective and cognitive engagement of students. PEGEGOG [Internet]. 2022 Jan. 2 [cited 2025 Oct. 4];12(1):207-12. Available from: https://www.pegegog.net/index.php/pegegog/article/view/1466