The extension of effective quark models à la Nambu-Jona Lasinio
to hadronic interactions is a powerful tool to predict the
hadron parameters in the low energy region, i.e. 
GeV.
Within this framework the quark-resonance model fully takes into account
the nonlocality of the effective interactions through a derivative expansion
in inverse powers of the ultraviolet cutoff 
.
The bosonization of the lowest dimensional four-quark operators leads to the ENJL model, while the inclusion of higher dimensional multiquark operators generates next-to-leading corrections to the leading ENJL contributions to the parameters of the effective low energy meson Lagrangian.
Next-to-leading power corrections to the leading logarithms proportional
to 
have
been explicitely calculated for the two-point vector correlation
function. They can be written in terms of two new coefficients
which are fixed by experimental data.
Their numerical relevance in the energy region 
MeV
has been shown in this case.
The type of corrections we have analyzed are not the only ones:
next-to-leading corrections in the 
expansion and gluonic
corrections can be present to bridge the remaining gap with experimental
data.