  We consider a non-linear realization of the electroweak symmetry-breaking
pattern $SU(2)_L\times SU(2)_R/SU(2)_{L+R}$ to construct a low-energy effective
theory, later extended by the inclusion of heavy new-physics resonances. After
assuming appropriate high-energy constraints given by Weinberg sum-rules and
the asymptotic behaviour of form-factors, we obtain relations between resonance
masses and some low-energy effective couplings. These predictions are compared
with current experimental data and some resonance mass bounds are inferred.
