Pardede , B. H. ., S. . Tampubolon, and F. D. . Lestari. “The Effect of Using Group Chat Discussion on Whatsapp Into Students’ Vocabulary Mastery Seventh Grade at SMP St Yoseph Medan”. Jurnal Pendidikan Dan Konseling (JPDK), vol. 4, no. 6, Dec. 2022, pp. 12386-95, doi:10.31004/jpdk.v4i6.10460.