**Question 1.**
Does Élie Cartan's paper
Les groupes réels simples, finis et continus,
Ann. Sci. École Norm. Sup. (3) 31 (1914), 263–355
contain a classification of $\Bbb C$-linear involutions of simple complex Lie algebras?

**Question 2.**
If not, what kind of a similar/related classification does it contain?

**Question 3.**
In what book/paper is this Cartan's paper discussed?

MathSciNet contains only the title, while zbMATH contains a review: a translation into German of a few lines from the introduction.

skew-linear involution? In any case it is never explicit (the paper doesn't mention automorphisms). And all along it makes this classification, which is equivalent to classifying those skew-linear involutions (more than half of the paper is about exceptional cases EFG). I don't think it gives any information on linear involutions. $\endgroup$ – YCor Jun 30 '20 at 14:20real structures(anti-linear involutions). However, conjugacy classes of of real structures bijectively correspond to conjugacy classes of $\Bbb C$-linear involutions. See page 442 of Helgason's book, or Serre, Cohomologie galoisienne, III.4.5, Theorem 6 and Example (b). Helgason writes that Cartan discovered this later, in 1929. $\endgroup$ – Mikhail Borovoi Jun 30 '20 at 17:10