“THE IMPLEMENTATION OF PROBLEM BASED LEARNING MODEL TO INCREASE STUDENTS™ MATHEMATICAL PROBLEM SOLVING FOR GRADE VIII AT SMP NEGERI 37 MEDAN 2019 2020”. JURNAL HANDAYANI PGSD FIP UNIMED, vol. 10, no. 2, Dec. 2019, pp. 90-98, https://doi.org/10.24114/jh.v10i2.16054.