Fedorchuk, V. M., & Fedorchuk, V. I. (2003). On new differential equations of the first order in the space M(1,4) × R(u) with non-trivial symmetries. Annales Universitatis Paedagogicae Cracoviensis Studia Mathematica, 3, 49–53. Retrieved from https://studmath.uken.krakow.pl/article/view/13466