Abstract.
By L(G) we denote a line graph of G.
We set L0(G)=G.
Then for i>0 the i-iterated line graph of G is
Li(G)=L(Li-1(G)).
Further, by C(G) we denote the subgraph of G induced by
central vertices.
Let G be a graph such that L2(G) is not
empty.
Then there is a supergraph H of G such that