Introduction to Mathematical Logic, Sixth Edition
《Introduction to Mathematical Logic, Sixth Edition》 · 印刷第 1 页 Section 1.1「The Classical Groups」的定义及第 11 页 Section 1.1.4 末的覆盖群约定；保留本书的实数、复数、四元数语境与范围约定
The classical groups are the groups of invertible linear transformations of finite-dimensional vector spaces over the real, complex, and quaternion fields, together with the subgroups that preserve a volume form, a bilinear form, or a sesquilinear form (the forms being nondegenerate and symmetric or skew-symmetric). […] We have now completed the list of the classical groups associated with $\mathbb R$, $\mathbb C$, and $\mathbb H$. We will return to this list at the end of the chapter when we consider real forms of complex algebraic groups. Later we will define covering groups; any group covering one of the groups on this list—for example, a spin group in Chapter 7—will also be called a classical group.