Iranian Mathematical Society (IMS) Bulletin of the Iranian Mathematical Society 1017-060X 34 No. 1 2011 01 20 σ-Normality of Topological Spaces37 44 en M. Mirzavaziri 2011 01 20 Normal σ-obtaiable Couple topological space σ-normal Semicontinuous σ-continuous σ-Urysohn’s lemma