Fort space on real numbers is not cozero complemented

[Moniker1998]

#1049 @prabau

[prabau]

I think we should add a separate paragraph like the following at the beginning:

"Note that in any normal space the cozero sets are exactly the open $F_\sigma$-sets (Corollary 1.5.13 of {{Engelking ...}}). This is the case in $X$ since {S154|P13}."

Then the second sentence of the next paragraph can be simplified slightly:

"Then $U$ is an open $F_\sigma$-set in $X$ and hence a cozero set."

And in the refs: section, replace the existing ref with Engelking.

[Moniker1998]

@prabau what do you mean by {{Engelking ...}} ?

[GeoffreySangston]

@Moniker1998 I believe change {{Engelking : ...}} to {{zb:0684.54001}}.

In github dot dev, you can use the search feature to find other examples of this usage to confirm the style is correct. I.e., type in: {{zb

[Moniker1998]

@prabau ready for review