The USSR Olympiad Problem Book: Selected Problems and Theorems of Elementary Mathematics by D. O. Shklarsky, N. N. Chentzov, and I. M. Yaglom This book contains 320 unconventional problems in algebra, arithmetic, elementary number theory, and trigonometry. Most of the problems first appeared in competitive examinations sponsored by the School Mathematical Society of the Moscow State University and the Mathematical Olympiads held in Moscow.