"`Gerla (University of Salerno, Italy), in this book, is concerned with fuzzy logic in the narrow sense, as the subtitle ""Mathematical Tools for Approximate Reasoning"" makes clear. The preface indicates that the book is principally concerned with three mathematical tools: the theory of fuzzy closure operators, an extension principle for closure operators, and the theory of recursively enumerable fuzzy subsets. Gerla sets out the details of his research related to these tools. Obviously, this book is intended for advanced study in graduate courses and as a resource for researchers, and so it would be a good addition to libraries of institutions where graduate studies and research in FLn are carried out. Graduate students and faculty' R. Bharath, emeritus, Northern Michigan University in Choice, January 2002"