[1]
N. A. Kachanovsky, “Biorthogonal Appell-like systems in a Hilbert space”, MFAT, vol. 2, no. 3, pp. 36–52, Dec. 1996, Accessed: Dec. 19, 2025. [Online]. Available: https://zen.imath.kiev.ua/index.php/mfat/article/view/18