Example 3

Tag 03T7, permanent. Cite it as [Bourbaki, Tag 03T7].

Theory of Sets, chapter III, § 3. Equipotent sets. Cardinals

$\mathrm{Card}(\{\emptyset, \{\emptyset\}\})$ is denoted by 2; this is the cardinal of every set consisting of two distinct elements.

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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