P. Billingsley, Probability and Measure, John Wiley and Sons, New York, 1885.
 B. Furtula and I. Gutman, A forgotten topological index, J. Math. Chem. 53 (4) (2015) 1184–1190.
 M. Gordon and G. R. Scantlebury, Non-random polycondensation: statistical theory of the substitution effect, Trans. Faraday Soc. 60 (2) (1964) 604–621.
 I. Gutman, On the origin of two degree-based topological indices, Bull. Acad. Serbe Sci. Arts (Cl. Sci. Math. Natur.) 146 (2014) 39–52.
 I. Gutman and N. Trinajstić, Graph theory and molecular orbitals. Total π-electron energy of alternant hydrocarbons, Chem. Phys. Lett. 17 (1972) 535–538.
 P. Hall and C. C. Heyde, Martingale Limit Theory and its Application, Academic Press, New York, 1980.
 R. Nikolić , I. M. Tolić, M. Trinajstić and I. Baucić, On the Zagreb indices as complexity indices, Croatica Chemica Acta 73 (2000) 909–921.
 J. R. Platt, Inuence of neighbor bonds on additive bond properties in paraffins, Chem. Phys. 15 (1947) 419–420.
 S. K. Simić and B. Zhou, Indices of trees with a prescribed diamater, Appl. Anal. Discrete Math. 1 (2007) 446–454.
 R. T. Smythe and H. Mahmoud, A survey of recursive trees, Theory Probab. Math. Statist. 51 (1995) 1–27.