A study of the p-d model by means of the COM is reported in Refs. [1,90,91,92,93]. In particular the following properties have been computed:
The COM results have been compared with the ones obtained by:
The p-d model has been studied in the context of the COM by considering different approximations. The so-called reduced p-d model, where the transitions to the lower Hubbard band are neglected, has been analyzed in Refs. [1,90,91]. In these papers different choices of the basic composite fields have been taken. In Ref.  the effect of the local antiferromagnetic correlations on the electronic properties, density of states and band dispersions, has been analyzed as a function of the hole doping. The chosen basic operators reproduce the exact single-site results.
In Ref.  the spin correlator has been self-consistently calculated by means of a sum rule with the content of the Pauli principle; the calculated local magnetic moment agrees well with the data obtained by numerical simulation.
In Ref.  we have enlarged the basic field by considering on the same foot both spin and charge correlations. As a result the set of equations to determine all the correlators closes and a fully self-consistent formulation is obtained.
The complete p-d model has been studied in Refs. [92,93] in a four-pole approximation. The density of states shows the Zhang-Rice singlet band situated around the chemical potential. The dispersion of this band gives a Fermi surface which is in good agreement with the experimental results for . Several quantities, the local magnetic moment, the chemical potential, the d- and p- particle densities and the charge-transfer susceptibility, are in excellent agreement with the numerical results.