V. Jeba Rani, S. Sundar Raj, and T. Shyla Isaac Mary. “Non-Adjacent Vertex Sum Polynomial of Umbrella Graphs, Jahangir Graph, Tadpole Graph and Lollipop Graph”. Malaya Journal of Matematik, vol. 9, no. 01, Jan. 2021, pp. 941-4, https://www.malayajournal.org/index.php/mjm/article/view/1201.