2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/217618We tackle the problem of estimating a regression function observed in an instrumental regression framework. This model is an inverse problem with unknown operator. We provide a spectral cut-off estimation procedure which enables to derive oracle inequalities which warrants that our estimate, built without any prior knowledge, behaves as well as, up to $\log$ term, if the best model were known.Statistics Theory62G05; 62G20text