BlackmoreD., PrykarpatskyA. K., PrykarpatskyYa. A., and SamoilenkoA. M. 2019. “Theory of Multidimensional Delsarte – Lions Transmutation Operators. II”. Ukrains’kyi Matematychnyi Zhurnal 71 (6), 808-39. https://umj.imath.kiev.ua/index.php/umj/article/view/1478.