Yildirim, O., and S. Caglak. “On the Lie Symmetries of the Boundary Value Problems for Differential and Difference Sine-Gordon Equations”. Bulletin of the Karaganda University. Mathematics Series 102, no. 2 (June 30, 2021): 142–153. Accessed March 5, 2026. https://mts.buketov.edu.kz/mathematics-vestnik/article/view/427.