  We present a comparative analysis of chiral quark models which include
nonlocal covariant four-fermion couplings. We consider two alternative ways of
introducing the nonlocality, as well as various shapes for the
momentum-dependent form factors governing the effective interactions. In all
cases we study the behavior of model parameters and analyze numerical results
for constituent quark masses and quark propagator poles. Advantages of these
covariant nonlocal schemes over instantaneous nonlocal schemes and the standard
NJL model are pointed out.
