Pardede BH, Tampubolon S, Lestari FD. The Effect of Using Group Chat Discussion on Whatsapp Into Students’ Vocabulary Mastery Seventh Grade at SMP St Yoseph Medan. JPDK [Internet]. 2022 Dec. 21 [cited 2025 Dec. 15];4(6):12386-95. Available from: https://journal.universitaspahlawan.ac.id/index.php/jpdk/article/view/10460