Wandini, R., Damanik, E., & Iskandar, W. (2019). Analysis of Problem Solving Ability Students Mathematis PGMI UINSU Based Zone of Proximal Development Of Students Primary School. Proceeding Of International Conference On Islamic Education (ICIED), 4(1), 182-185. Retrieved from http://conferences.uin-malang.ac.id/index.php/icied/article/view/1083