Before revision:  Moreover, we show that the same remains true even within the class of planar graphs in the case k \geq } 3. Additionally, we examine the computational complexity of several graph problems restricted to CPG graphs . In particular, we show that Independent Set and Clique Cover remain NP-hard for B_0-CPG graphs.
After revision:  Moreover, we show that the same remains true even within the class of planar graphs in the case k \geq } 3. Additionally, we examine the computational complexity of several graph problems restricted to CPG graphs and show, in particular, that Independent Set and Clique Cover remain NP-hard for B_0-CPG graphs.