References
- Bank , S. 1987 . A note on zeros of solutions of w′ + P(z)w = 0 where P is a polynomial . Applicable Analysis , 25 : 29 – 41 .
- Strodt , W. 1954 . Contributions to the asymtotic theory of ordinary differential equations in the complex domain . Mem.Amer.Math.Soc , 13