\begin{circus}
	\circchannel a, b, c, d : \nat
\end{circus}

\begin{circus}
	\circprocess ExtInt \circdef \circbegin
\end{circus}
\begin{circusaction}
	\circspot ((a.4 \then \Skip) \intchoice (b.4 \then \Skip)) \extchoice ((a.4 \then \Skip) \intchoice (b.4 \then \Skip)) 
\end{circusaction}
\begin{circus}	
	\circend
\end{circus}

