Wulandari, Siti, et al. “EFEKTIVITAS MODEL PROBLEM BASED LEARNING DAN DISCOVERY LEARNING BERBANTUAN TANGRAM TERHADAP KEMAMPUAN PEMECAHAN MASALAH MATEMATIKA SISWA SMP”. Prosiding Seminar Nasional Matematika Dan Pendidikan Matematika, vol. 4, Aug. 2019, pp. 379-87, https://conference.upgris.ac.id/index.php/senatik/article/view/83.