  In a U(3)x U(3) quark chiral model of the Nambu-Jona-Lasinio type with the 't
Hooft interaction, the ground scalar isoscalar mesons and a scalar glueball are
described. The glueball (dilaton) is introduced into the effective meson
Lagrangian written in a chirally symmetric form on the base of scale
invariance. The singlet-octet mixing of scalar isoscalar mesons and their
mixing with the glueball are taken into account. Mass spectra of the scalar
mesons and glueball and their strong decays are described.
