PISZCZEK, M. On a multivalued second order differential problem with Jensen multifunction. Annales Universitatis Paedagogicae Cracoviensis Studia Mathematica, [S. l.], v. 8, p. 31–41, 2009. Disponível em: https://studmath.uken.krakow.pl/article/view/13257. Acesso em: 31 oct. 2026.