Mufliharsi, Risa, and Heppy Atma Pratiwi. “POLITENESS PRINCIPLE: PRESIDENT JOKO WIDODO’S SPEECH ACT IN VIDEO BLOG”. Bahtera: Jurnal Pendidikan Bahasa Dan Sastra, vol. 18, no. 1, Jan. 2019, pp. 79-92, doi:10.21009/BAHTERA.181.07.