Rayanto, Y. H. “The Effectiveness of Supplemental Exercises Textbook on Comprehending Morphemes”. Jurnal Educazione : Jurnal Pendidikan, Pembelajaran Dan Bimbingan Dan Konseling, vol. 7, no. 2, Nov. 2019, pp. 86-94, https://ejurnal.uij.ac.id/index.php/EDU/article/view/605.