How to Solve It: A New Aspect of Mathematical Method
In mathematics, the method of thinking is more important than the answer.
Introduction to Topology: Second Edition
As you study mathematics for a longer period, you'll find that the higher the level of abstraction in a theory, the wider its applicability.
What Exactly Is "Graph Theory" in Mathematics?
In mathematics, graphs are a central object of study in discrete mathematics. In many branches of mathematics (combinatorics, probability, topology, etc.), graphs serve as essential tools.
The Best Introductory Book on Ordinary Differential Equations
An accessible and progressive introduction that explains complex yet essential concepts in ordinary differential equations to undergraduate students majoring in mathematics, engineering, and science, all without compromising mathematical rigor.
Why Does Mathematics Become More Confusing in College?
When studying advanced mathematics, it is best to have a broad perspective. I recommend checking out *All the Math You Missed: But Need to Know for Graduate School*. Although this book is intended for graduate students, college freshmen can also read it in advance (without going through it as rigorously as a textbook) to develop a global view of mathematics.