Lopatin A. K. “Certain Aspects of Theoretical-Group Approach in Problems of Nonlinear Mechanics”. Ukrains’kyi Matematychnyi Zhurnal 44, no. 1 (February 4, 1992): 22-33. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/2317.