PETRINA, D. Ya. Model BCS Hamiltonian and Approximating Hamiltonian in the Case of Infinite Volume. IV. Two Branches of Their Common Spectra and States. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 55, n. 2, p. 174–196, 2003. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3899. Acesso em: 5 dec. 2025.