Zulkardi, Prahmana RCI, Putri RII. In memory of Jan de Lange and Kees Hoogland: Honoring their legacy and contributions to mathematics education in Indonesia. j. math. educ. [Internet]. 2025 Jul. 27 [cited 2025 Jul. 28];16(2):753-62. Available from: https://jme.ejournal.unsri.ac.id/index.php/jme/article/view/3839