Also, The Art of Problem Solving and mathlinks.ro are message boards where olympiad contestants publish solutions from almost every contest in the world. The Art of Problem Solving also publishes special textbooks geared towards olympiad students such as this one on Precalculus.
I want to prepare for the maths olympiad and I was wondering if you can recommend me some books about combinatorics, number theory and geometry at a beginner and intermediate level. I would appreciate your help.
One of my favorite mathematical olympiad books is this one: -Olympiad-Challenges-Titu-Andreescu/dp/0817645284by Andreescu and Gelca. It's more on the itermediate level. It is sort of a compilation on useful techniques with sample problems. I suggest you give it a go.
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