Nishikawa, Tomoko, and Guido Izuta. “RELATIONSHIP AMONG STUDENTS’ FACING PROBLEM RELATED MATHEMATICS LEARNING AND LESSON”. Humanities & Social Sciences Reviews 7, no. 2 (March 19, 2019): 156-164. Accessed July 8, 2020. https://giapjournals.com/hssr/article/view/hssr.2019.7216.