Introduction to Representation Theory
《Introduction to Representation Theory》 · 第 180 页 · Chapter 7，Section 7.2「Functors」，Example 8
More generally, if $\pi$ is a representation of $S_n$, we have functors $V \mapsto \operatorname{Hom}_{S_n}(\pi, V^{\otimes n})$. Such functors are called the Schur functors. Thus, the irreducible Schur functors are labeled by Young diagrams.