such that the subgraph induced by V' is connected
and has the property P.
Cardinality of the induced connected subgraph, i.e., .
Not approximable within
if P is a non-trivial hereditary graph property that
is satisfied by all paths and is false for some complete bipartite graph
(for example path, tree, planar, outerplanar, bipartite, chordal, interval)
NPO PB-complete when P is either path or chordal .
NPO PB-complete and not approximable within
when P is simple cycle .