Primeiro parágrafo do Prefácio deste livro:
"Students of mathematics and computer science often have trouble the first time the're asked to work seriously with mathematical proofs, because they don't know the "rules of the game". What is expected of you if you are asked to prove something? What distinguishes a correct proof from an incorrect one? This book is intended to help students learn the answers to these questions by spelling out the underlying principles involved in the construction of proofs."