HANGOS, K. M.; TUZA, Z.; YEO, A. Some Complexity Problems on Single Input Double Output Controllers. BRICS Report Series, [S. l.], v. 8, n. 18, 2001. DOI: 10.7146/brics.v8i18.20475. Disponível em: https://tidsskrift.dk/brics/article/view/20475. Acesso em: 20 aug. 2022.