Commutative Algebra with a View Toward Algebraic Geometry
《Commutative Algebra with a View Toward Algebraic Geometry》 · 第 479 页 · Exercise 19.9
An ideal $I\subset R$ is said to be perfect if the inequality of Corollary 18.5 is an equality for $M=R/I$; that is, if $\operatorname{depth}(I,R)=\operatorname{pd}_R R/I$.