Some Useful Books:
Advanced Mathematical Methods for Scientists and Engineers I Asymptotic Methods and Perturbation Theory by Bender and Orszag
Perturbation Methods by Hinch
Asymptotic Analysis by Murray
Mathematical Analysis by Apostol
Introduction to Perturbation Techniques by Nayfeh
Perturbation Methods for Engineers and Scientists by Bush
Complex Analysis: An Introduction to the Theory of Analytic Functions of One Complex Variable by Ahlfors
I Want to be a Mathematician by Halmos
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