Elida Purba, Chairul Umam, Azhar,. “The Rheological Characteristics of Dammar Mata Kuching”. Journal of Engineering and Scientific Research 2, no. 2 (December 28, 2020): 97–101. Accessed July 7, 2022. https://jesr.eng.unila.ac.id/index.php/ojs/article/view/50.