1. Recurrence in Topological Dynamics. Furstenberg Families and Ellis Actions;Akin,1997
2. A new kind of compactness for topological spaces;Bernstein;Fund. Math.,1970
3. Ultrafilters: where topological dynamics=algebra=combinatorics;Blass;Topology Proc.,1993
4. General Topology;Engelking,1989
5. Recurrence in Ergodic Theory and Combinatorial Number Theory;Furstenberg,1981