PIĄTEK, B. Riemann integrability of a nowhere continuous multifunction. Annales Universitatis Paedagogicae Cracoviensis Studia Mathematica, [S. l.], v. 7, p. 5–13, 2008. Disponível em: https://studmath.uken.krakow.pl/article/view/13264. Acesso em: 29 oct. 2026.