1. I. Schur, J. Reine Angew. Math. 147, 205 (1916); J. Reine Angew. Math. 148, 122 (1918).
2. L. Baratchart, S. Kupin, V. Lunot, and M. Olivi, J. Anal. Math. 114, 207 (2011).
3. V. I. Buslaev, Sb. Math. 210 (11), 1563 (2019).
4. V. I. Buslaev, Sb. Math. 206 (12), 1707 (2015).
5. G. Pólya, Sitzungsberichte Akad. Berlin, 55 (1929).