“…Landau hydrodynamics provides a plausible description for the evolution of the dense hot matter produced in high-energy heavy-ion collisions. Its dynamics during the first stage of the one-dimensional longitudinal expansion can be solved exactly and the one-dimensional longitudinal expansion problem admits simple approximate solutions [6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22]. The subsequent three-dimensional motion can be solved approximately to give rise to predictions that come close to experimental data [1,2,3,6,7].…”