A criterion of singularity formation for the non-isentropic gas dynamics   equations
  For the 1D non-isentropic polytropic gas dynamics equations we find sufficient and necessary conditions for blow up of derivatives in the terms of Cauchy data. In particular, the method allows to determine exact class of initial data corresponding to globally smooth in time solution. 
Olga S. Rozanova
math-ph math.AP math.MP