Algebra for College Student

Algorithm

Approximation

Improvement

### Books

Geometry For Colldge Students (Best Book)

Euclid and Beyond by Hartshorn

Geometry Revisited

Introduction to Geometry

Introduction to the Geometry of Complex Numbers

Problem Solving strategies for Math Olympiads

Solving Mathematical Problems by Terrance Tao

IMO Competition

Problem Solving by Halmos

More books for USAMO... Available here