  We review the so called A-scaled Nambu-Jona-Lasinio model both in the vacuum
and at finite temperature and density in the case of three flavors. Starting
from QCD and integrating out the gluons, we show how to reintroduce some of
their effects in order to take into account the trace (or scale) anomaly of
QCD. The axial U_A(1) anomaly is also present in the model in order to discuss
the eta' particle. In the present work we treat the pseudoscalar and scalar
sectors, pointing out the defects related to the omission of the vector
particles. We use our model to study the restoration of chiral symmetry as a
function of temperature, the thermodynamical functions and the equation of
state, and we survey the mixing between the scalar isoscalar particles and the
glueball.
