Memoirs of the American Mathematical Society 1992; 111 pp; softcover Volume: 100 ISBN10: 0821825410 ISBN13: 9780821825419 List Price: US$31 Individual Members: US$18.60 Institutional Members: US$24.80 Order Code: MEMO/100/480
 The main results of this work can be formulated in such an elementary way that it is likely to attract mathematicians from a broad spectrum of specialties, though its main audience will likely be combintorialists, settheorists, and topologists. The central question is this: Suppose one is given an at most countable family of algebras of subsets of some fixed set such that, for each algebra, there exists at least one set that is not a member of that algebra. Can one then assert that there is a set that is not a member of any of the algebras? Although such a set clearly exists in the case of one or two algebras, it is very easy to construct an example of three algebras for which no such set can be found. Grinblat's principal concern is to determine conditions that, if imposed on the algebras, will insure the existence of a set not belonging to any of them. If the given family of algebras is finite, one arrives at a purely combinatorial problem for a finite set of ultrafilters. If the family is countably infinite, however, one needs not only combinatorics of ultrafilters but also set theory and general topology. Readership Combinatorists, settheorists and general topologists. Reviews "A fascinating new angle that shows that nonmeasurable sets are here to stay."  The Bulletin of Mathematics Books and Computer Software Table of Contents  Introduction
 Main results
 Fundamental idea
 Finite sequences of algebras (1)
 Countable sequences of algebras (1)
 Proof of Theorem II
 Improvement of Theorem II (Proof of Theorem II*)
 Proof of Theorems III and IV
 The inverse problem
 Finite sequences of algebras (2)
 Countable sequences of algebras (2)
 Improvement of some main results
 Sets not belonging to semilattices of subsets and not belonging to lattices of subsets
 Unsolved problems
