Siallagan, E. W.; Ahda, A.; Bangun, A. E. B.; Tindaon, S. G. G.; Manik, N. A. Smartphone Use and Students’ Concentration in Class: A Qualitative Study at SMP Negeri 27 Medan. OJE 2026, 6 (1), 48-55. https://doi.org/10.61730/7eddkm92.