Corollary 5.1.7.8. Suppose we are given a commutative diagram of simplicial sets
\[ \xymatrix@R =50pt@C=50pt{ \operatorname{\mathcal{C}}\ar [rr]^-{F} \ar [dr]_{U} & & \operatorname{\mathcal{D}}\ar [dl]^{V} \\ & \operatorname{\mathcal{E}}, & } \]
where $U$ and $V$ are inner fibrations and $\operatorname{\mathcal{E}}= \Delta ^ n$ is a standard simplex. Then $F$ is an equivalence of inner fibrations over $\operatorname{\mathcal{E}}$ if and only if it an equivalence of $\infty $-categories.