Irwanto, J. ., Kurniati, D. ., Yudianto, E. ., & Santoso, K. A. . (2025). Assessing university student’s Van Hiele level of abstract thinking in-two variable linear equations using IRT: Implication for Economic Education. International Journal of Innovative Research and Scientific Studies, 8(9), 113–126. https://doi.org/10.53894/ijirss.v8i9.10633