PIĄTEK, B. Some properties of convex and *-concave multifunctions. Annales Universitatis Paedagogicae Cracoviensis Studia Mathematica, [S. l.], v. 5, p. 77–86, 2006. Disponível em: https://studmath.uken.krakow.pl/article/view/13294. Acesso em: 29 oct. 2026.