“…Recently, the approach of the adiabatic exponent limit has been well carried out for example in [15, 31, 34-36, 48, 49]. In addition, there are still some other very effective methods [9,16,17,23,25,27] to deal with the related problems of δ-shocks. Finally, it is necessary to point out that delta shock wave has also been found in other hyperbolic models, such as in the nonlinear chromatography [20], in the shallow water dynamics [18], in the thin film [28] and also in the porous media [13].…”