Harahap, Fitri Annisa, Saidun Hutasuhut, and Thamrin Thamrin. “Development of Flip Book-Based Economics Teaching Materials To Improve The Economic Learning Outcomes of Students In Class Xi Man 2 Deli Serdang In Academic Year 2021 2022”. Journal Research of Social Science, Economics, and Management 2, no. 6 (January 19, 2023): 938–956. Accessed December 5, 2025. https://jrssem.publikasiindonesia.id/index.php/jrssem/article/view/356.