Introduction to Mathematical Logic, Sixth Edition
《Introduction to Mathematical Logic, Sixth Edition》 · 第 575 页 · Chapter 12，Section 12.3.2「Examples of Iwasawa Decompositions」
The information is summarized in the Satake diagram, which is obtained from the Dynkin diagram of $\mathfrak g$ by the following procedure: (S1) If a simple root vanishes on $\mathfrak a$, then the corresponding node in the Dynkin diagram is marked by $\bullet$. (S2) The simple roots that have nonzero restriction to $\mathfrak a$ correspond to nodes that are marked by $\circ$; if two simple roots have the same restriction to $\mathfrak a$, then the corresponding nodes are joined by a double-pointed arrow.