DYMARSKII, Ya. M. On manifolds of self-adjoint elliptic operators with multiple eigenvalues. Methods of Functional Analysis and Topology, [S. l.], v. 7, n. 2, p. 68–74, 2001. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/151. Acesso em: 17 dec. 2025.