Remark 1

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

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

It may happen that squares (12) and (14) are cartesian without square (13) being so (I, p. 139, exerc. 2).

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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