If you find a PDF, ask yourself if you truly need permanent ownership. Often, the act of purchasing a rare used copy or borrowing a physical book from a library will give you more motivation to study than a free digital file hidden in a downloads folder. Respect the intellectual labor of Professor Lee Peng Yee. His work has produced decades of competent mathematicians—use it ethically and diligently.

Happy proving.

His contribution to mathematics education goes beyond a single textbook. Professor Lee was instrumental in curriculum development for the International Baccalaureate (IB) and various pre-university programs. He is also a leading expert in the history of Chinese mathematics.