Bourbaki

Remark 1

Tag 020A, permanent. Cite it as [Bourbaki, Tag 020A].

Topologie algébrique, chapter IV, § 1. Espaces délaçables

There exist topological spaces B, connected and locally arcwise connected, such that certain points aa of B, but not all, possess a neighbourhood V such that the homomorphism of π1(V,a)\pi_1(V, a) into π1(B,a)\pi_1(B, a) is trivial (III, p. 336, exerc. 6).

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.