TEXTORIUS, Björn. Minimaxprinzipe zur Bestimmung der Eigenwerte $J$-nichtnegativer Operatoren. MATHEMATICA SCANDINAVICA, [S. l.], v. 35, p. 105–114, 1974. DOI: 10.7146/math.scand.a-11538. Disponível em: https://tidsskrift.dk/math/article/view/11538. Acesso em: 13 aug. 2026.