The super line graph

In Bagga et al. (1995) the authors introduced the concept of the super line graph of index r of a graph G, denoted by Lr(G). The vertices of Lr(G) are the r-subsets of E(G) and two vertices S and T are adjacent if there exist s∈S and t∈T such that s and t are adjacent edges in G. In this paper, some properties of super line graphs of index 2 are presented, and L2(G) is studied for certain classes of graphs.