Siregar HM, Turmudi, Nurjanah, Darhim. Representational Difficulty Across Cognitive Stages in Quadratic Functions: An APOS–Newman Analysis. IJCRSEE [Internet]. 2026 Aug. 31 [cited 2026 Oct. 20];14(2):317-29. Available from: https://ijcrsee.com/index.php/ijcrsee/article/view/3662