On Sombor Index of Unicyclic and Bicyclic Graphs

Gutman proposed a topological index called the Sombor index, which was defined as Formula: see text where Formula: see text is the degree of the vertex Formula: see text in graph Formula: see text. In this paper, we determine the second-minimum and second-maximum values of the Sombor index over all the unicyclic graphs of order Formula: see text and bicyclic graphs of order Formula: see text.