Gultom, Jelita, Midun Siagian, Ucok Jhon Royagus Tamba, Jecky Bukit, and Murniaty Simorangkir. “The Extract Salaon (Indigofera Tinctoria L) Leaf As the Natural Dye of Ulos in Keeping for the Batak Culture Values”. Jurnal Pendidikan Kimia 9, no. 2 (August 31, 2017): 293–298. Accessed July 5, 2025. https://jurnal.unimed.ac.id/2012/index.php/jpk/article/view/7602.