Sitanggang, Andri Kristianto, Asrin Lubis, and Tetty Suyanty Elisa. “PENGEMBANGAN MODEL DESIGN DIDACTIC RESEARCH (DDR) UNTUK MENGATASI HAMBATAN BELAJAR (LEARNING OBSTACLE) MATEMATIKA”. JURNAL HANDAYANI PGSD FIP UNIMED 15, no. 1 (June 20, 2024): 1–6. Accessed July 5, 2025. https://jurnal.unimed.ac.id/2012/index.php/handayani/article/view/60118.