KRZYWKOWSKI, M. A more colorful hat problem. Annales Universitatis Paedagogicae Cracoviensis Studia Mathematica, [S. l.], v. 10, p. 67–78, 2011. Disponível em: https://studmath.uken.krakow.pl/article/view/13218. Acesso em: 11 nov. 2026.