Geodesic
Even Covers and Collectionwise Normal Spaces
Canadian journal of mathematics, Tome 30 (1978) no. 3, pp. 466-473

Voir la notice de l'article provenant de la source Cambridge University Press

The concept of an even cover is introduced early in elementary topology courses and is known to be valuable. Among other facts it is known that X is paracompact if and only if every open cover of X is even. In this paper we introduce the concept of an n-even cover and show its usefulness. Using n-even we define an embedding that on closed subsets is equivalent to collectionwise normal. We also give sufficient conditions for a point finite open cover to have a locally finite refinement and also sufficient conditions for this refinement to be even. Finally we show that the collection of all neighborhoods of the diagonal of X is a uniformity if and only if every even cover is normal. This last result is particularly interesting in light of the fact that every normal open cover is even. 
Shapiro, H. L.; Smith, F. A. Even Covers and Collectionwise Normal Spaces. Canadian journal of mathematics, Tome 30 (1978) no. 3, pp. 466-473. doi: 10.4153/CJM-1978-041-6
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