Yang D-C, Chang M-C, Sianturi IA. The Study of Addition and Subtraction for Two Digit Numbers in Grade One Between Singapore and Taiwan. Am J Edu Learn [Internet]. 2017 Apr. 25 [cited 2024 May 19];2(1):75-82. Available from: http://onlinesciencepublishing.com/index.php/ajel/article/view/21