PEETRE, Jaak. A generalization of Courant’s nodal domain theorem. MATHEMATICA SCANDINAVICA, [S. l.], v. 5, p. 15–20, 1957. DOI: 10.7146/math.scand.a-10484. Disponível em: https://tidsskrift.dk/math/article/view/10484. Acesso em: 14 aug. 2026.