1. "Principles of Mathematical Analysis" by Walter Ruding, this book is a must-read textbook for mathematics majors, with detailed and in-depth explanation and emphasis on the methods and ideas of proof. Especially for calculus, real analysis and complex analysis.
2. Author of linear algebra: Gilbert Strong. This book introduces the concepts of matrix and its operation, vector, linear transformation and linear space. The theory is rigorous and the content is rich, which is suitable for most linear algebra courses.
3. The Course of Ordinary Differential Equations was written by Derhan M in America. This book covers the basic knowledge, analytical solutions and numerical methods of ordinary differential equations, and is suitable for university mathematics departments to explain ordinary differential equations and higher-order ordinary differential equations.
4. Probability and Statistics is written by Sheldon M. Ross. This book expounds the basic theory of probability and statistics in detail through probability distribution, expectation, random variables and random processes. This paper expounds the application research methods of probability and statistics theory in engineering and science, which is suitable for university statistics and related scientific fields.
These extracurricular books cover different learning fields of mathematics, which are very helpful for students to understand and master the concepts of college mathematics, and can also expand students' mathematical thinking ability and solve practical mathematical problems.