Dalimunthe, R. A., and E. K. Hasibuan. “The Effect of the APOS Approach Assisted by GeoGebra on State Islamic Junior High School Students’ Spatial Skills in Geometric Transformations”. Journal of Mathematics Instruction, Social Research and Opinion, vol. 5, no. 3, Sept. 2026, pp. 2469–2478, doi:10.58421/misro.v5i3.2164.