Fuangfoo, Phornpen, and Narumon Changsri. 2020. “STUDENTS’ MATHEMATICAL FLEXIBILITY THINKING IN MATHEMATICS CLASSROOM USING LESSON STUDY AND OPEN APPROACH”. Journal of MCU Nakhondhat 7 (12). Nakhon Si Thammarat, Thailand:41-56. https://so03.tci-thaijo.org/index.php/JMND/article/view/249094.