ALBEVERIO, S.; AYUPOV, S.; RAKHIMOV, A.; DADAKHODJAEV, R. Index theory for real factors. Eurasian Mathematical Journal, [S. l.], v. 3, n. 2, p. 12–20, 2012. Disponível em: https://emj.enu.kz/index.php/main/article/view/788. Acesso em: 31 oct. 2025.