HARWANTO, Untung Nugroho. WHAT MAKES INTRODUCTORY PHYSICS DIFFICULT?. Jurnal Saintika Unpam : Jurnal Sains dan Matematika Unpam, [S. l.], v. 2, n. 1, p. 28–37, 2019. DOI: 10.32493/jsmu.v2i1.2916. Disponível em: https://openjournal.unpam.ac.id/index.php/jsmu/article/view/2916. Acesso em: 3 feb. 2026.