defined a graph M(G) as an intersection graph
O(F) on the vertex-set V(G) of any graph G. Let X(G) be the edge-set of G and
F = V'(G)O X(G) where V'(G) indicates the family of one-point subsets of the
set V(G). Let M(G)= O(F). M(G) is called the middle graph of G