Krisnamurti, C. N. “Efforts to Increase Student Activity and Learning Outcomes With Flat Building Materials Using the Problem-Based Learning (PBL) Learning Model”. Edumaspul: Jurnal Pendidikan, Vol. 8, no. 1, Mar. 2024, pp. 1545-9, https://ummaspul.e-journal.id/maspuljr/article/view/7867.