TITLE: Nice book on integrals
QUESTION [13 upvotes]: On this site I usually see very amazing techniques to solve integrals; contour integrals, differentiating under the integral sign, transforming the integral into a series and son on and so forth.
What I really like is that seemingly difficult integrals become very easy to evaluate; you just need this "a-ah" moment and the right technique.
I know that this skill must be trained, so I would like to find a book or a website which has a collection of such integrals.
I don't mean just difficult integrals, for which you have to work through pages of calculations; I want integrals that are easy to solve if you know how to apply the right technique
Can somebody point me in the right direction?

REPLY [17 votes]: Here are some reference sources:

Inside Interesting Integrals by Paul J. Nahin
A Treatise on Integral Calculus Volume 1 and Volume 2 by  Joseph Edwards
Superhuman Integration Techniques by Andre Kessler
Integration: The Feynman Way
Wikipedia: Differentiation Under The Integral Sign
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