KAIRIES, H.-H. Spectra of certain operators and iterative functional equations. Annales Universitatis Paedagogicae Cracoviensis Studia Mathematica, [S. l.], v. 2, p. 13–22, 2002. Disponível em: https://studmath.uken.krakow.pl/article/view/13507. Acesso em: 30 oct. 2026.