“…Indeed, if at the initial time, there are no gas-dynamic perturbations in the medium, then z (1) = 0, z (1) ξ = 0, and c 0 p 0ξ > 0 (is determined only by the initial conditions) and the last term on the left side of the third equation (11) far exceeds the remaining terms related to the spatial derivatives. Conversely, once the moment of shock-wave formation is approached, the gradient of the gas-dynamic perturbations tends to infinity and the quantity c 0 p 0ξ > 0 is bounded (determined only by the initial conditions) and gas-dynamic nonlinearity plays the major role.…”