D. Blackmore, A. K. Prykarpatsky, Y. A. Prykarpatsky, and A. M. Samoilenko, “Theory of multidimensional Delsarte – Lions transmutation operators. II”, Ukr. Mat. Zhurn., vol. 71, no. 6, pp. 808–839, Jun. 2019, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/1478