  Admissible perturbations (i.e., perturbations that do not change the
Mironenko reflecting function of the system) are obtained for an autonomous
three-dimensional quadratic generalized Langford system with five parameters.
The obtained non-autonomous perturbed systems retain many of the qualitative
properties of solutions of the original system. In particular, the instability
(in the sense of Lyapunov) of the equilibrium point, the presence of a periodic
solution and its asymptotic stability (instability) are proved for perturbed
systems. The presence of similar chaotic attractors in the original and
perturbed systems is shown by numerical simulation.
