How are normal and T4 spaces defined in books?


A recent discussion on PlanetMath has led me to consider how various sources define normal and T4 spaces. I limited myself to books, mostly textbooks. No articles were consulted. As will be seen from the table below, there is no agreement on the question of how to define it. I am not giving precise references at this time, and may choose to never do that. I think the abbreviated form may be sufficient for those that seek to check what I have done. If you want to add something to the table, file a correction. S refers to the condition that closed setsPlanetmathPlanetmath can be separated by open sets. The condition S is due to Tietze, according to Alexandroff and Hopf. Of course, T1 + S is the same as T2 +S.

Source Normal T4 Page Year
Alexandroff and Hopf T1+S T1+S 68 1935
Wilder S ? 49 1949
Kelley S T1+S 112 1955
Hocking and Young T1+S T1+S 41 1961
Pervin S T1+S 88 1964
Gaal T1+S S 87 1964
Lipschutz S T1+S 141 1965
Husain T1+S S 7 1966
Dugundji T2+S T2+S 144 1966
Gemignani T1+S S 102 1967
Willard S T1+S 99 1970
Steen and Seebach T1+S S 12 1970
Maunder S - 15 1970
Munkres T1+S - 195 1975
Morris S T2+S 121 1988
Repovš T1+S S 6 1998
Stroppel T2+S S 6 2006
Title How are normal and T4 spaces defined in books?
Canonical name HowAreNormalAndT4SpacesDefinedInBooks
Date of creation 2013-03-22 17:09:12
Last modified on 2013-03-22 17:09:12
Owner Mathprof (13753)
Last modified by Mathprof (13753)
Numerical id 12
Author Mathprof (13753)
Entry type Topic
Classification msc 54D15
Related topic UrysohnsLemma
Related topic T4Space