d
subgraph</i> is a subgraph formed by specifying a set of vertices
<i>V'</i> and then selecting all of the edges from the original graph
that connect two vertices in <i>V'</i>. So in this case <i>E' = {(u,v)
in E: u,v in V'}</i>.  Figure 1 shows a graph <i>G<sub>0</sub></i> and
two subgraphs <i>G<sub>1</sub></i> and <i>G<sub>2</sub></i>. The edge
set for <i>G<sub>1</sub></i> is <i>E<sub>1</sub> = { (E,F), (C,F)
}</i> and the edge set for <i>G<sub>2</sub></i> is <i>E<sub>2</sub> =
{ (A,B) }</i>. Edges such 