  Ground and first radially excited scalar isoscalar meson states and a scalar
glueball are described in a nonlocal U(3)xU(3) quark model. The glueball is
introduced into the effective meson Lagrangian by means of the dilaton model on
the base of the scale invariance of the meson Lagrangian. The scale invariance
breaking by current quark masses and gluon anomalies is taken into account. The
glueball anomalies turn out to be important for the description of the
glueball-quarkonia mixing. The masses of five scalar isoscalar meson states and
their strong decay widths are calculated. The state f_0(1500) is shown to be
composed mostly of the scalar glueball.
