on the extremal connective eccentricity index among trees with maximum degree

The connective eccentricity index (cei) of a graph g is defined as ξ^ce(g) = ∑ v∈v (g) dg^(v)/εg^(v) , where dg^(v) is the degree of v and εg(v) is the eccentricity of v. in this paper, we characterize the unique trees with the maximum and minimum cei among all n-vertex trees and n-vertex conjugated trees with fixed maximum degree, respectively.