  Taking into account the negative results of direct searches for beyond the
Standard Model fields and the consequent mass gap between Standard Model and
possible unknown states, the use of electroweak effective theories is
justified. Whereas at low energies we consider a non-linear realization of the
electroweak symmetry breaking with a singlet Higgs and a strongly-coupled
ultraviolet completion, at higher energies the known particles are assumed to
be coupled to heavy states: bosonic fields with $J^P=0^\pm$ and $J^P=1^\pm$ (in
electroweak triplets or singlets and in QCD octets or singlets) and fermionic
states with $J=\frac{1}{2}$ (in electroweak doublets and in QCD triplets or
singlets). By integrating out these heavy resonances, the pattern of
next-to-leading order low-energy constants among the light fields can be
studied. A phenomenological study trying to estimate the scale of these
resonances is also shown.
