Remark

Tag 01P8, permanent. Cite it as [Bourbaki, Tag 01P8].

Topologie algébrique, chapter I, § 4. Revêtements

A continuous, separated, open, proper mapping with finite fibres is not necessarily a covering. This is the case for the mapping $x\mapsto x^2$ of $\mathbf{R}$ into $[0; +\infty [$ .

Bourbaki sets the proof directly after the statement, and the corpus does not separate them, so what is above is the statement and its proof together.

Cited by

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Cites

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