Taufiq, Wahyu, and Vidya Mandarani. “Buku Ajar Let’s Learn English Progressively”. Umsida Press (August 22, 2021): 1-157. Accessed November 21, 2024. https://press.umsida.ac.id/index.php/umsidapress/article/view/978-979-3401-72-0.