Naive Lie Theory
《Naive Lie Theory》 · 印刷第 21 页 Chapter 2 章首域的约定、第 101 页 Section 6.2「Parabolic subgroups and Borel subgroups」节首对象约定及 Lemma 6.2.2 前的定义段（省略中间内容）
$k$ is an algebraically closed field and $F$ a subfield. All algebraic varieties are over $k$. […] In this section $G$ is a linear algebraic group over $k$. […] A closed subgroup $P$ of $G$ is a parabolic subgroup, or is parabolic, if the quotient variety $G/P$ is complete.