Marbun, Sukses, 		Saragih, Berlin, AND 		Hasballah, Hasballah.
" RANCANG BANGUN MESIN PENGUPAS KULIT ARI BIJI KOPI KAPASITAS 30 KG/JAM" <em>Jurnal Teknologi Mesin UDA</em> [Online], Volume 2 Number 1 (30 June 2021)