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Ehlers Henry J.. Logic: modern and traditional . Charles E. Merrill Publishing Company, Columbus, Ohio, 1976, viii + 245 pp.

Part Three (49 pp.) is devoted to the main decidability and undecidability results concerning Chomsky's grammars and to a short exposition of complexity of decidable properties. The book is mathematically very clear and elegant. Many exercises (mainly of a theoretical character) allow the reader to verify his comprehension of the material. The book can be recommended to readers with an abstract mathematical orientation. It can be an excellent basic reference for courses in mathematics departments and a good supplementary reference for courses in computer science departments. Reading this book will be a pleasure for everybody who can appreciate good mathematics.