$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
9.12
\begin{equation} \begin{gathered}\label{equation:compact-in-categorical-pullback} \xymatrix@R =50pt@C=50pt{ \operatorname{\mathcal{C}}_{\pm } \ar [r]^-{ E_{+} } \ar [d]^{ E_{-}} & \operatorname{\mathcal{C}}_{+} \ar [d]^{F_{+}} \\ \operatorname{\mathcal{C}}_{-} \ar [r]^-{F_{-}} & \operatorname{\mathcal{C}}. } \end{gathered} \end{equation}