Bourbaki

Corollary

Tag 01N5, permanent. Cite it as [Bourbaki, Tag 01N5].

Topologie algébrique, chapter I, § 2. Applications étales

Let B be a topological space. The fibre product of two étale B-spaces is an étale B-space.

Let (E,p)(E, p) and (E′,p′)(E', p') be étale B-spaces. The mapping pr1:E×B_1: E\times_B E′→EE'\rightarrow E is étale (prop. 8), hence the mapping p∘p\circ pr1:E×BE′→B_1: E\times_BE'\rightarrow B is étale (prop. 6, a)).

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.

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Cites

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Machine translation of the English, by gpt-5.4, against glossary version 34. Not checked by a person.