Ussapan, Chaidilok, and Dr.Tatchawat Laosuwan. 2021. “The Development of Learning Activities by Open Approach on the Topic Political Regime to Enhance Problem Solving Ability of Mathayom Suksa 4 Students”. KKU Research Journal (Graduate Studies) Humanities and Social Sciences 9 (3):84-95. https://so04.tci-thaijo.org/index.php/gskkuhs/article/view/248231.