Fig. 4.

(i) The network on $X=\{a,b,c,d\}$ is semi-resolved, compressed tree-sibling but not stable. (ii) The network on $X=\{a,b,c\}$ is binary, stable but not tree-sibling. (iii) The network on $X=\{a,b,c,d\}$ is non-binary, tree-child but not stable