  We recently observed the iso-singlet scalar sigma(600)-particle and the
iso-doublet scalar kappa(900)-particle, through the re-analyses of pi pi- and K
pi-scattering phase shifts, respectively. First, assuming the two iso-singlet
states, the sigma(600) and the established f0(980), being the ideal mixing
states n n and s s, respectively, of a single scalar nonet, it is pointed out
that the mass value of the iso-singlet flavor-octet state, obtained from the
orthogonal transformation, satisfies, together with the kappa(900) and the
iso-triplet scalar a0(980)-particle, the Gell-Mann Okubo mass-formula.
Furthermore, it is argued that, by investigating their properties of masses and
widths, this scalar sigma-nonet, together with the pseudo-scalar pi-nonet,
realizes the linear representation of SU(3) chiral symmetry.
