Bose_einstein Correlations of Unstable Particles
  Within a field theoretical formalism suited to treat inhomogeneous hot quantum systems, we derive the two-particle correlation function for particles having a spectral width gamma in the region of their emission. We find, that this correlation function measures the radius R0 of the thermal source only in case gamma*R0 > 1. 
P.A.Henning and Ch.Hoelbling