Saftari M, Darmawijoyo D, Hartono Y. Development of student activities sheet based on apos theory to understand the concept of Riemann sum. Math Didactic [Internet]. 15 Mei 2020 [dikutip 2 Juli 2025];6(1):110-23. Tersedia pada: https://jurnal.stkipbjm.ac.id/index.php/math/article/view/914