Figure 2.

(A): A graph representation of a KPD program with a two-way exchange cycle, where ${\mathcal{V}}_p=\{1,2\}$ and $\mathcal{E}=\left\{\right(1,2),(2,1\left)\right\}$; (B): A graph representation of a KPD program with a three-way exchange cycle, where ${\mathcal{V}}_p=\{1,2,3\}$ and $\mathcal{E}=\left\{\right(1,2),(2,3),(3,1\left)\right\}$; (C): A graph representation of a NEAD chain, where ${\mathcal{V}}_a=\left\{1\right\},{\mathcal{V}}_p=\{2,3\}$ and $\mathcal{E}=\left\{\right(1,2),(2,3\left)\right\}$; donor 3 at the end of the chain becomes a bridge donor.