Remark 1

Tag 0AN9, permanent. Cite it as [Bourbaki, Tag 0AN9].

Lie Groups and Lie Algebras, chapter IV, § 2. Tits Systems

We shall see in no. 5 (Cor. of Th. 3) that, if $(G, B, N)$ is given, there exists at most one subset $S$ of $N/(B \cap N)$ such that $(G, B, N, S)$ is a Tits system.

Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.

Cited by

Nothing.

Cites

Cor. of Th. 3