Blackmore, D., A. K. Prykarpatsky, Ya. A. Prykarpatsky, and A. M. Samoilenko. “Theory of Multidimensional Delsarte – Lions Transmutation Operators. I”. Ukrains’kyi Matematychnyi Zhurnal 70, no. 12 (December 25, 2018): 1660–1695. Accessed April 26, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/1667.