2019 Let G be a simple graph with vertex set V=V(G)={v_1,v_2,…,v_n} and edge set E=E(G). For v_i ϵ V(G), by d_i=d_i (G) we denote the degree (number of neighbors) of the vertex v_i. The second Zagreb index is defined as M_2 (G)=∑_(v_i v_j ϵE(G))=〖d_i d_j 〗. In this paper, we study the minimal and maximal second Zagreb index of trees with fixed diameter. info:eu-repo/semantics/article https://phaidrabg.bg.ac.rs/o:29014 ISSN: 0340-6253 All rights reserved On Kirchhoff Index, Laplacian Energy and Their Relations eng Keywords:Graph energy, Kirchhoff index, Laplacian energy application/pdf 330044 bytes MATCH Communications in Mathematical and in Computer Chemistry 81(2) Milovanović, Igor Milovanović, Emina Glogić, Edin Matejić, Marjan