FEDORCHUK, V. M.; FEDORCHUK, V. I. 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, [S. l.], v. 3, p. 49–53, 2003. Disponível em: https://studmath.uken.krakow.pl/article/view/13466. Acesso em: 30 oct. 2026.