Pramasdyahsari, Agnita, Rina Setyawati, and Irkham Albab. “Connecting University Mathematics and School Mathematics to Address Klein’s Double Discontinuity: A Case of Ring Theory”. Beta: Jurnal Tadris Matematika 12, no. 2 (November 30, 2019): 122-132. Accessed May 30, 2020. https://jurnalbeta.ac.id/index.php/betaJTM/article/view/336.