Nihayaturrahmah, Siti. 2018. “Improving Students Activity and Students Learning Outcomes by Using Problem Centered Learning (PCL) Setting Numbered Head Together (NHT)”. Jurnal Axioma : Jurnal Matematika Dan Pembelajaran 3 (1):60-75. https://ejurnal.uij.ac.id/index.php/AXI/article/view/310.