\begin{tabular}{cc}	
		\begin{tikzpicture}	
			\draw[fill=black](0,0)circle(2pt);
			\draw[fill=black](1,0)circle(2pt) node[right] {\scriptsize $(s,t-1)$};
			\draw[fill=black](0,1)circle(2pt) node[left] {\scriptsize $(s-1,t)$};
			\draw[fill=black](1,1)circle(2pt) node[right] {\scriptsize $(s,t)$};
			\draw[->,>=triangle 45,rounded corners=9pt,shorten >=2pt] (0,1)--(1,1)--(1,0) ;
			\node[above] at (0.5,1) {$W(s,t)$};
			\node[right] at (1,0.5) {$(-1)$};
		\end{tikzpicture}&
		\begin{tikzpicture}
			\draw[fill=black](0,0)circle(2pt);
			\draw[fill=black](1,0)circle(2pt) node[right] {\scriptsize $(s,t-1)$};
			\draw[fill=black](0,1)circle(2pt) node[left] {\scriptsize $(s-1,t)$};
			\draw[fill=black](1,1)circle(2pt) node[right] {\scriptsize $(s,t)$};
			\draw[->,>=triangle 45,rounded corners=9pt,shorten >=2pt] (1,0)--(1,1)--(0,1) ;
			\node[above] at (0.5,1) {$W(s,t)^{-1}$};
			\node[right] at (1,0.5) {$(-1)$};
		\end{tikzpicture}
	.
	\end{tabular}