Napitupulu, K. ., B. Munthe, and N. Siregar. “The Effect of Reinforcement Skills on Increasing the Learning Motivation of Grade XI Students in Christian Religious Education”. PIJAR: Jurnal Pendidikan Dan Pengajaran, vol. 4, no. 1, Nov. 2025, pp. 68-79, doi:10.58540/pijar.v4i1.1124.