[4] Z. Nehari:
Univalent functions and linear differential equations. Lectures on functions of a complex variable. The Univ. Michig. Press, Ann Arbor 1955, 49 - 60.
MR 0069874 |
Zbl 0066.32602
[6] G. Birkhoff G.-С. Rota: Ordinary differential equations. Boston 1962.