On extremal Sombor index of trees with a given dissociation number $\phi$

The Sombor index is a topological index in graph theory defined by Gutman in 2021. In this article, we find the maximum Sombor index of trees of order $\mathbf{n}$ with a given dissociation number $\phi$, where $\text{ceil}\ast \frac{2\mathbf{n}}{3}\le \phi (G)\le \mathbf{n}-1$. We also provide the unique graph among the chosen class where the maximum Sombor index is attained.