Algebraic Geometry
《Algebraic Geometry》 · 第 184 页 · Chapter III，Section 8「Some Local Algebra」
If $A$ is a ring, and $M$ is an $A$-module, recall that a sequence $x_1,\ldots,x_r$ of elements of $A$ is called a regular sequence for $M$ if $x_1$ is not a zero divisor in $M$, and for all $i=2,\ldots,r$, $x_i$ is not a zero divisor in $M/(x_1,\ldots,x_{i-1})M$.