Hutabarat, N.M. and Simorangkir, M. 2025. Pengembangan E-modul Pembelajaran Kimia Berbasis Problem Based Learning Pada Materi Sistem Periodik Unsur. Reflection Journal. 5, 2 (Sep. 2025), 709–717. DOI:https://doi.org/10.36312/rj.v5i2.3300.