Reni Tania, and Welven Aida. “PENGARUH MODEL PEMBELAJARAN PROBLEM BASED LEARNING TERHADAP KEMAMPUAN BERPIKIR KRITIS SISWA KELAS IX MATA PELAJARAN IPS DI SMP NEGERI 1 BANGUN PURBA”. Bakoba : Journal of Social Science Education, vol. 1, no. 1, Jan. 2021, pp. 24-33, https://journal.upp.ac.id/index.php/bakoba/article/view/587.