Simanjuntak, Sihardo R. H., et al. “The Effect of Role-Play and Brainstorming Technique on Students’ Speaking Achievement”. Cetta: Jurnal Ilmu Pendidikan, vol. 2, no. 3, Aug. 2019, pp. 554-66, https://jayapanguspress.penerbit.org/index.php/cetta/article/view/1926.