A. N. (Andrei? Nikolaevich) Kolmogorov (1903-87) was a prominent Russian mathematician who made significant contributions to many areas of math, including probability theory, topology, logic, turbulence, and mechanics. His other Dover books are Introductory Real Analysis, Elements of the Theory of Functions and Functional Analysis (with S.V. Fomin), and Mathematics, Its Content, Methods and Meaning (with A. D. Aleksandrov and M. A. Lavrent'ev). In his many years on the faculty of Moscow State University, Dr. Kolmogorv's doctoral students included several who became prominent 20th-century mathematicians.