There is a black stamp on the top of the book, but there is no problem with reading it. Please purchase only if you understand. A set of 5 reference books explaining the basic theorems and theories of mathematics. - Title 1: Theorems of Mathematics You Should Know - Title 2: Pythagorean Triangles and Their Doctrines - Title 3: The History of Circular Reasoning and Its Theories - Title 4: Number Theory of Sunflowers - Title 5: Inequalities Thank you for viewing.