The degree distance index (DDI) is a vertex-degree weighted version of well-known that called by Wiener (WI). In extremal theory graphs, improving the bounds with best possible values worth investigating problem. this note, exact formulae DDI for four different types sum graphs in terms various indic...

Let G be a simple connected graph and {v_1,v_2,..., v_k} be the set of pendent (vertices of degree one) vertices of G. The reduced distance matrix of G is a square matrix whose (i,j)-entry is the topological distance between v_i and v_j of G. In this paper, we compute the spectrum of the reduced distance matrix of the generalized Bethe trees.