1. 1. L. V. Ovsiannikov, Group Analysis of Differential Equations [in Russian], Nauka, Moscow (1978)
2. [in English]: Acad. Press, New York (1982).
3. 2. A. V. Pogorelov, The Minkowski Multidimensional Problem [in Russian], Nauka, Moscow (1975).
4. 3. V. M. Fedorchuk, V. I. Fedorchuk, "On classification of the low-dimensional non-conjugated subalgebras of the Lie algebra of the Poincare group P(1,4)," in: Symmetry and Integrability of the Equations of Mathematical Physics, Collection of Works of Institute of Mathematics, NAS of Ukraine, 3, No. 2, 301-307 (2006) (in Ukrainian).
5. 4. V. M. Fedorchuk, V. I. Fedorchuk, "Reduction of the (1+3)-dimensional inhomogeneous Monge-Ampère equation to first-order partial differential equations," Ukr. Mat. Zh., 74, No. 3, 418-426 (2022), https://doi.org/10.37863/umzh.v74i3.6996