Emery vs. Hubbard model for cuprate superconductors: a composite operator method study Adolfo Avella, Ferdinando Mancini, Francesco Paolo Mancini and Evgeny Plekhanov Eur. Phys. J. B, 86 6 (2013) 265 Published online: 12 June 2013 DOI: 10.1140/epjb/e2013-40115-3