101
[231] If \(X\) is filtering, βa neighborhood of \(β\) in \(X\)β is a subset \(Uβ X\) such that
\[ β kβ X β jβ X,jβ₯ k β jβ U~ . \]
[231] If \(X\) is filtering, βa neighborhood of \(β\) in \(X\)β is a subset \(Uβ X\) such that