R. Rohini, and G. Srividhya. “Some Connectivity Eccentric Indices and Modified Eccentric Indices of Benzenoid $H_k$ System”. Malaya Journal of Matematik, vol. 9, no. 01, Jan. 2021, pp. 431-7, https://www.malayajournal.org/index.php/mjm/article/view/1054.