Strøm's theorem

Let $(X,A)$ and $(Y,B)$ be NDR-pairs. Their product in the category of topological pairs

$$(X\times Y,X\times B\cup A\times Y)$$

is also an NDR-pair.

Revised on December 3, 2009 23:12:57
by Toby Bartels
(173.60.119.197)