(Int) |
A-B |
\begin{gather} x_{1} x_{2} + x_{1}^{2} x_{2}^{2} + x_{3},\label{E:mm1} \\ x_{1} x_{3} + x_{1}^{2} x_{3}^{2} + x_{2},\tag{\ref{E:mm1}a}\\ x_{1} x_{2} x_{3};\tag{\ref{E:mm1}b} \end{gather}
\begin{subequations}\label{E:gp} \begin{gather} x_{1} x_{2} + x_{1}^{2} x_{2}^{2} + x_{3},\label{E:gp1}\\ x_{1} x_{3} + x_{1}^{2} x_{3}^{2} + x_{2},\label{E:gp2}\\ x_{1} x_{2} x_{3},\label{E:gp3} \end{gather} \end{subequations}
\[ \begin{CD} A @>>> B \\ @VVV @VVV\\ C @= D \end{CD} \]