*定義 [#ia4ed2a7]
A topological space is ultranormal if any two disjoint closed subsets are contained in disjoint clopen subsets.

*性質 [#fbf4cdd0]

*注意 [#v5aa7675]

*出典 [#a592b77c]
Robert L. Ellis, ''Extending continuous functions on zero-dimensional spaces'', Mathematische Annalen 186. [[http://www.springerlink.com/content/u545572g8u66652k/>http://www.springerlink.com/content/u545572g8u66652k/]]