Introduction to Mathematical Logic, Sixth Edition
《Introduction to Mathematical Logic, Sixth Edition》 · 第 490 页 · Chapter 11，Section 11.1.5「Exercises」，Exercise 5(b)
Suppose $G = \mathrm{SL}(n, \mathbb C)$. Find $N$ in this case. The group $G/N$ is denoted by $\mathrm{PSL}(n, \mathbb C)$ (the projective linear group).