@article{costa_bermudez_bershad_2002,  title={The performance surface in nonlinear mean square estimation: application to active noise control problems with correlated signals},  volume={13},  ISSN={0103-1759},  url={https://doi.org/10.1590/S0103-17592002000100008},  DOI={10.1590/S0103-17592002000100008},  number={1},  journal={Sba: Controle & Automação Sociedade Brasileira de Automatica},  publisher={Sociedade Brasileira de Automática},  author={Costa, Márcio H. and Bermudez, José C. M. and Bershad, Neil J.},  year={2002},  month={Jan},  pages={68–76} }