Kerodon

\begin{equation} \begin{gathered}\label{equation:levelwise-pullback-for-cartesian} \xymatrix { \overline{\mathscr {F}} \ar [d]^{ \overline{\gamma } } \ar [r] & \underline{C} \ar [d]^{ \underline{f} } \\ \overline{\mathscr {G}} \ar [r] & \underline{D}, } \end{gathered} \end{equation}