[1]
Y. G. Kondratiev, J. L. Silva, and L. Streit, “Generalized Appell systems”, MFAT, vol. 3, no. 3, pp. 28–61, Sep. 1997, Accessed: Dec. 19, 2025. [Online]. Available: https://zen.imath.kiev.ua/index.php/mfat/article/view/42