A note on perfectly orderable graphs (Q1917281)

A graph \(G\) is called a \(D\)-graph if each of its induced subgraphs contains a vertex \(x\) such that, for any edge \(yz\) with \(y\), \(z\) not neighbours of \(x\), \(y\) dominates \(z\) or vice versa, which means \(N(y)-\{z\}\subseteq N(z)\). Here the author proves that each \(D\)-graph is perfectly orderable.