The energy of a graph is defined as the sum of the absolute values of the eigenvalues of the graph. Let (PR denote the class of trees with a perfect matching on n vertices. F. Zhang, H. Li [On acyclic conjugated molecules with minimal energies, Discrete Appl. Math. 92(1999) 71-84] have determined trees with minimal, second-minimal and third-minimal energies in (P. In this paper, using the quasiordering relation, we discuss the trees in (l havi...
