On the Relativistic Description of the Nucleus
  We present here a formalism able to generalise to a relativistically covariant scheme the standard nuclear shell model. We show that, using some generalised nuclear Green's functions and their Lehmann representation we can define the relativistic equivalent of the non relativistic single particle wave function (not loosing, however, the physical contribution of other degrees of freedom, like mesons and antinucleons). It is shown that the mass operator associated to the nuclear Green's function can be approximated with the equivalent of a shell-model potential and that the corresponding ``single particle wave functions'' can be easily derived in a specified frame of reference and then boosted to any other system, thus fully restoring the Lorentz covariance 
R. Cenni and G. Vagradov