Kanguzhin, Baltabek, Lyalilya Zhapsarbayeva, and Zhumabay Madibaiuly. “Lagrange Formula for Differential Operators and Self-Adjoint Restrictions of the Maximal Operator on a Tree”. Eurasian Mathematical Journal 10, no. 1 (March 30, 2019). Accessed October 9, 2025. https://emj.enu.kz/index.php/main/article/view/137.