References
- Complex Analysis L. V. Ahlfors
- Advanced Mathematical Methods for Scientists and Engineers C. M. Bender;S. A. Orszang
- Elementary Differential Equations(fifth ed.) W. E. Boyce;R. C. DiPrima
- Lecture Notes in Mathematics Asymptotics of Analytic Difference Equations G. K. Immink
- Principles of Applied Mathmatics, Transformation and Approximation J. P. Keener
- Acta Mathematica v.100 Regular Iteration of Real and Complex Functions G. Szekeres
- Asymptotic Expansions for Ordinary Differential Equations W. Wasow