  Based on a recently derived effective chiral meson Lagrangian from the
extended SU(2)\otimes SU(2) Nambu -- Jona-Lasinio (ENJL) model, in the linear
realization of chiral symmetry, we extract to leading order in the 1/N_c
expansion all associated relevant three-point functions \rho \to \pi\pi, \sigma
\to \pi\pi, a_1 \to \rho\pi, a_1 \to \sigma\pi, as well as the amplitude for
\pi\pi scattering. We discuss the formal differences of these amplitudes as
compared with those derived in the literature and calculate the associated
decay widths and scattering parameters. The differences have two origins: i)
new terms, which are proportional to the current quark mass and arise from
taking the correct NJL vacuum from the first steps in a proper-time expansion,
are present in the Lagrangian; ii) an implemented chiral covariant treatment of
the diagonalization in the pseudoscalar - axialvector sector induces new
couplings between three or more mesonic fields. Both effects have been derived
from the chiral Ward Takahashi identities, which are fully taken into account
at each order of the proper-time expansion.
