GorgulaV.I. and GürbüzN. 2015. 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. 67, 3 (Mar. 2015), 333–340.