Kerodon

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4.22
\begin{equation} \begin{gathered}\label{equation:categorical-pullback-square5} \xymatrix@R =50pt@C=50pt{ X_{01} \ar [r] \ar [d] & X_0 \ar [d]^{q} \\ X_1 \ar [r] & X } \end{gathered} \end{equation}