OSPANOV, K. N.; AKHMETKALIYEVA, R. D. Some Inequalities for Second Order Differential Operators with Unbounded Drift. Eurasian Mathematical Journal, [S. l.], v. 6, n. 2, p. 63–74, 2015. Disponível em: https://emj.enu.kz/index.php/main/article/view/608. Acesso em: 19 sep. 2025.