Melo, Gilberto Pechoto, et al. “Fault Detection Using State Observers With Unknown Input, Identified by Orthogonal Functions”. VETOR - Revista De Ciências Exatas E Engenharias, vol. 22, nº 1, janeiro de 2013, p. 38-56, https://furg.emnuvens.com.br/vetor/article/view/1028.