Introduction to Lie Algebras and Representation Theory
《Introduction to Lie Algebras and Representation Theory》 · 第 102 页 · Chapter 19「The Exceptional Lie Algebras」导言
In Chapter IV the classification of root systems was completed. There are four infinite families: $A_l, B_l, C_l, D_l$, and five exceptional systems: $G_2, F_4, E_6, E_7, E_8$. [...] The remaining exceptional algebras can be constructed in a unified way, as was shown by Tits and Freudenthal.