BAYASGALAN, T. The numerical range of linear relations in spaces with an indefinite metric. Математическая физика, анализ, геометрия, Харків, Україна, v. 7, n. 1, p. 115–118, 2000. Disponível em: https://mag.ilt.kharkiv.ua/index.php/mag/article/view/m07-0115e. Acesso em: 4 груд. 2024.