$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
4.81
\begin{equation} \begin{gathered}\label{equation:coskeleton-vs-homotopy} \xymatrix@R =50pt@C=50pt{ \operatorname{\partial \Delta }^ m \ar [d] \ar [r]^-{\sigma _0} & \operatorname{cosk}^{\circ }_{n}(\operatorname{\mathcal{C}}) \ar [d]^{q} \\ \Delta ^ m \ar@ {-->}[ur] \ar [r]^-{\overline{\sigma }} & \mathrm{h}_{\mathit{\leq n}}\mathit{(\operatorname{\mathcal{C}})} } \end{gathered} \end{equation}