Lie Groups Beyond an Introduction - Anthony W. Knapp - Google Books,proof explanation - Knapp, Lie Groups: beyond an Introduction, Theorem II.2.15 - Mathematics Stack Exchange,Lie Groups, Lie Algebras, and Representations: An Elementary Introduction | SpringerLink,Introduction to Lie Algebras (Springer Undergraduate Mathematics Series): Erdmann, K., Wildon, Mark J.: 9781846280405: Amazon.com: Books,Nilpotent Lie Groups