  Experimental spectra of the CERN/SPS experiments NA44 and NA49 are fitted
while using four different equations of state of nuclear matter within a
relativistic hydrodynamic framework. For the freeze-out temperatures, $T_f =
139$ MeV and $T_f = 116$ MeV, respectively, the corresponding freeze-out
hypersurfaces and Bose-Einstein correlation functions for identical pion pairs
are discussed. It is concluded, that the Bose-Einstein interferometry measures
the relationship between the temperature and the energy density in the equation
of state of nuclear matter at the late hadronic stage of the fireball
expansion. It is necessary, to use the detailed detector acceptances in the
calculations for the Bose-Einstein correlations.
