Khumkhong P, Ugsornkid S, Somchaipeng T. Effects of Using Open Approach on Mathematical Problem-Solving Ability of Arithmetic Series of 11th Grade Students. IARJ [internet]. 2024 Oct. 17 [cited 2026 Oct. 2];4(5):437-52. available from: https://so03.tci-thaijo.org/index.php/IARJ/article/view/278069