BIYAROV, B. N. On Volterra Relatively Compact Perturbations of the \( \text{Laplace operator} \). Eurasian Mathematical Journal, [S. l.], v. 5, n. 1, p. 135–140, 2014. Disponível em: https://emj.enu.kz/index.php/main/article/view/566. Acesso em: 9 oct. 2025.