SAVIN, A.; ZHUIKOV, K. η-Invariant and Index for Operators on the Real Line Periodic at Infinity. Eurasian Mathematical Journal, [S. l.], v. 12, n. 3, p. 57–77, 2021. DOI: 10.32523/2077-9879-2021-12-3-57-77. Disponível em: https://emj.enu.kz/index.php/main/article/view/226. Acesso em: 30 sep. 2026.