Naive Lie Theory
《Naive Lie Theory》 · 第 271 页 · Chapter 16，Section 16.2.1 与 Proposition 16.2.2(i)
$G$ is quasi-split over $F$ if $D_0 = \emptyset$ and anisotropic if $D_0 = D$. [...] Proposition 16.2.2. (i) $G$ is quasi-split over $F$ if and only if there exists a Borel subgroup of $G$ that is defined over $F$.