  A collective treatment of the I=0 scalar mesons below 2 GeV [sigma (550),
f0(980), f0(1370), f0(1500) and f0(1710)] in a non-linear chiral Lagrangian
framework that is constrained by the mass and the partial decay widths of the
I=1/2,1 scalars [kappa(900), K0*(1430), a0(980) and a0(1450)] is presented. The
sub-structure of these states in terms of two and four quark components, as
well as a glueball component is explored, and its correlation with the mass of
f0(1370) is studied. Consistency with the available experimental data suggests
that the sigma(550) is dominantly a non-strange four-quark state, whereas the
sub-structure of other I=0 states are sensitive to the input mass of f0(1370).
This investigation estimates the scalar glueball mass in the range 1.47--1.64
GeV.
