Rukli, Rukli, Ma’rup Ma’rup, Erni Ekafitria Bahar, and Rezki Ramdani. 2021. “The Estimation of Test Item Difficulty Using Focus Group Discussion Approach on the Semantic Differential Scale”. Kasetsart Journal of Social Sciences 42 (3):599–606. https://so04.tci-thaijo.org/index.php/kjss/article/view/253487.