\begin{circus}
\circchannel a, b, c
\end{circus}
\begin{circus}
\circprocess P1 \circdef \circbegin
\end{circus}
\begin{circusaction}
\circspot
a \then b \then c \then \Skip
\end{circusaction}
\begin{circus}
\circend
\end{circus}
\begin{circus}
\circprocess P2 \circdef \circbegin
\end{circus}
\begin{circusaction}
\circspot
a \then b \then c \then \Skip
\end{circusaction}
\begin{circus}
\circend
\end{circus}
\begin{circus}
\circprocess P3 \circdef \circbegin
\end{circus}
\begin{circusaction}
\circspot
a \then b \then c \then \Skip
\end{circusaction}
\begin{circus}
\circend
\end{circus}
\begin{circus}
\circprocess P4 \circdef (P1 \interleave P2) \lpar \lchanset a \rchanset \rpar P3
\end{circus}