Freeze-out in hydrodynamical models in relativistic heavy ion collisions
  Freeze-out of particles across 3-dimensional space-time hypersurface with space-like normal is discussed in a simple kinetic model. The final momentum distribution of emitted particles shows a non-exponential transverse momentum spectrum, which is in quantitative agreement with recently measured SPS pion and $h^-$ spectra. 
V.K. Magas, Cs. Anderlik, L.P. Csernai, F. Grassi, W. Greiner, Y.   Hama, T. Kodama, Zs.I. Lazar, H. St\"ocker