  A celebrated 1922 theorem of Kuratowski states that there are at most 14
distinct sets arising from applying the operations of complementation and
closure, any number of times, in any order, to a subset of a topological space.
In this paper we consider the case of complementation and two abstract closure
operators. In contrast to the case of a single closure operation, we show that
infinitely many distinct sets can be generated, even when the closure operators
commute.

General Topology;Commutative Algebra