Zelenyuk, Yevhen. Ultrafilters and Topologies on Groups. Berlin, Boston: De Gruyter, 2011. Web. Retrieved 22 May. 2013, from http://www.degruyter.com/view/product/40405

Zelenyuk, Y. (2011). Ultrafilters and Topologies on Groups. Berlin, Boston: De Gruyter. Retrieved 22 May. 2013, from http://www.degruyter.com/view/product/40405

Zelenyuk, Yevhen. 2011. Ultrafilters and Topologies on Groups. Berlin, Boston: De Gruyter. Retrieved 22 May. 2013, from http://www.degruyter.com/view/product/40405