Corollary
Tag 08SO, permanent. Cite it as [Bourbaki, Tag 08SO].
Integration, IV, p. 42, § 4. Integrable functions and sets
If is a decreasing sequence of integrable sets, then .
For, if then is the lower envelope of the decreasing sequence (No. 3, Prop. 4).
Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.