Figure 9. A counter example illustrating that the converse to claim 2 in Proposition 4 may not be true.

Reactions ${\displaystyle a}$ and ${\displaystyle b}$ are parallel in $(\mu ,a,b)$. CGP maps the double-marked module $(\mu ,a,b)$ onto the minimal double-marked module $({\mu }^{\prime },a,b)$ where reactions ${\displaystyle a}$ and ${\displaystyle b}$ are not parallel.