Solitons: Differential equations, symmetries, and infinite-dimensional algebras
《Solitons: Differential equations, symmetries, and infinite-dimensional algebras》 · 第 567 页 · Appendix B，Section B.7「Integral ring extensions」
Let $B$ be an $A$-algebra. Then $A':=\{b\in B;b\text{ integral over }A\}$ is an $A$-subalgebra of $B$ which is called the integral closure of $A$ in $B$.