Bourbaki

Example 1

Tag 01M4, permanent. Cite it as [Bourbaki, Tag 01M4].

Topologie algébrique, chapter I, § 1. Produits fibrés et carrés cartésiens

The composite of two strict mappings is not necessarily strict. In fact, every continuous mapping f:X→Yf: X\rightarrow Y is the composite of the mapping pr2:X×Y→_2: X\times Y\rightarrow Y and of the mapping x↦(x,f(x))x\mapsto (x, f(x)) of X into X×YX\times Y, which are both strict (TG, I, p. 26, prop. 5 and TG, I, p. 25, cor. 2). On the other hand, the composite of two strict and injective (resp. surjective) mappings is a strict mapping.

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