Search for: [Subject and Keywords = Matematyka \-\- czasopisma.] OR [Title = Ultrafilters and ω1\-points in βN\\N] OR [Title = Ultrafilters and ω1\-points in βN\\N] OR [Creator = Balcar, Bohuslav \(1943– \)] OR [Creator = Balcar, Bohuslav \(1943– \)]