BRASCHE, J. F.; NIZHNIK, L. P. A generalized sum of the quadratic forms. Methods of Functional Analysis and Topology, [S. l.], v. 8, n. 3, p. 13–19, 2002. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/188. Acesso em: 18 dec. 2025.