TAHIR, M. B.; ASWHAD, A. A. On the Riesz Means of Expansions by Riesz Bases Formed by Eigenfunctions for the Ordinary Differential Operator of 4-th Order. Ibn AL-Haitham Journal For Pure and Applied Sciences, Baghdad, Iraq., v. 22, n. 1, 2017. Disponível em: https://jih.uobaghdad.edu.iq/index.php/j/article/view/1277. Acesso em: 29 mar. 2025.