Natthaphon Hongthong และ Teerachot Lokkathat; Narongsak Rorbkorb. (2024) Effect of Open Approach and Concrete-Pictorial-Abstract (CPA) Approach on Number Sense and Mathematical Achievement in Subtraction of Grade-1 Students. <i>Journal of Science and Science Education</i>, <i>7</i>(2), 433-445.Natthaphon Hongthong และ Teerachot Lokkathat; Narongsak Rorbkorb. "Effect of Open Approach and Concrete-Pictorial-Abstract (CPA) Approach on Number Sense and Mathematical Achievement in Subtraction of Grade-1 Students". Journal of Science and Science Education 7 (2024):433-445.Natthaphon Hongthong และ Teerachot Lokkathat; Narongsak Rorbkorb. Effect of Open Approach and Concrete-Pictorial-Abstract (CPA) Approach on Number Sense and Mathematical Achievement in Subtraction of Grade-1 Students. Faculty of Science, Ubon Ratchathani University:ม.ป.ท. 2024.