V. M. Gorbachuk, “On approximation of solutions of operator-differential equations with their entire solutions of exponential type”, MFAT, vol. 22, no. 3, pp. 245–255, Sep. 2016, Accessed: Dec. 16, 2025. [Online]. Available: https://zen.imath.kiev.ua/index.php/mfat/article/view/639