On Average Eccentricity

The average eccentricity has been used as a molecular descriptor since 1988. In this paper, we give lower and upper bounds for the average eccentricity in terms of the numbers of vertices and edges, give lower and upper bounds for average eccentricity of trees with fixed diameter, fixed number of pendent vertices and fixed matching number, respectively, and determine the n-vertex trees with the first four smallest and the first /2 th-largest n ´a average eccentricities for 6. nt