MAINKA-NIEMCZYK, E. Multivalued second order differential problem. Annales Universitatis Paedagogicae Cracoviensis Studia Mathematica, [S. l.], v. 11, p. 53–68, 2012. Disponível em: https://studmath.uken.krakow.pl/article/view/13210. Acesso em: 31 oct. 2026.