ค่อมบุญ ป, ภิรมจิตรผ่อง เ. A Development of Mathematics Problem Solving Skills Using Problem-Based Learning Plan for Prathom Suksa 2 Students in Schools under the Office of Ubon Ratchathani Primary Education Service Area 2 . ubonreseva [internet]. 2021 Aug. 28 [cited 2026 Oct. 3];4(2):23-30. available from: https://so06.tci-thaijo.org/index.php/ubonreseva/article/view/250983