The Characterization of Generalized Wreath Products

The main USC’ of wreath products in group theory has been to supply examples of groups with special properties, and applications of this sort are too numerous and well known to be listed here. It is well known that the wreath product has a certain universal property, which we may describe in the following way. If G is a transitive permutation group on a set S, if C is a G-congruence on S, and if x E S, then G induces, in a natural way, a permutation group