WOLDEAMANUEL, M.; ATAGANA, H.; ENGIDA, T. What makes chemistry difficult?. African Journal of Chemical Education, [S. l.], v. 4, n. 2, p. 31–43, 2014. Disponível em: https://www.ajol.info/index.php/ajce/article/view/104070. Acesso em: 15 oct. 2026.