Algebraic Geometry
《Algebraic Geometry》 · 第 110 页 · Chapter II，Section 5，Definition
Let $(X,\mathcal O_X)$ be a scheme. A sheaf of $\mathcal O_X$-modules $\mathcal F$ is quasi-coherent if $X$ can be covered by open affine subsets $U_i=\operatorname{Spec}A_i$, such that for each $i$ there is an $A_i$-module $M_i$ with $\mathcal F|_{U_i}\cong\widetilde M_i$.