Zuindra, Z., B. P. Chitra, and M. Geubrina. “‘English Polite Utterances’ Terhadap Siswa/I Kelas XII SMA Nurul Hasanah Medan”. JPM: Jurnal Pengabdian Masyarakat, vol. 1, no. 2, Nov. 2020, pp. 48-52, https://mail.djournals.com/jpm/article/view/109.