M. Melina, I. L. . . Pasaribu, and L. . . Simanjuntak, “The Analysis of Online Learning PKN in the Covid-19 Pandemic of SMP Negeri 2 Lintongnihuta Humbang Hasundutan Regency”, Mantik, vol. 5, no. 3, pp. 1775-1781, Nov. 2021.