Ramadhani, Rahmi. “The Enhancement of Mathematical Problem Solving Ability and Self-Confidence of Students through Problem Based Learning”. Jurnal Riset Pendidikan Matematika 5, no. 1 (May 18, 2018): 127–134. Accessed May 18, 2025. https://journal.uny.ac.id/index.php/jrpm/article/view/13269.