Gorgula, V. I., and N. Gürbüz. “Generalized Elastic Line Deformed on a Nonnull Surface by an External Field in the 3-Dimensional Semi-Euclidean Space $\mathbb{E}_1^3$”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 67, no. 3, Mar. 2015, pp. 333–340, https://umj.imath.kiev.ua/index.php/umj/article/view/1986.