Tolentino, M. A. C., and G. R. J. Eugenio. “On the Set Chromatic Number of the Middle Graph of Extended Stars and Related Tree Families: Discrete and Computational Geometry, Graphs, and Games”. Thai Journal of Mathematics, vol. 21, no. 4, Dec. 2023, pp. 835–853, https://thaijmath2.in.cmu.ac.th/index.php/thaijmath/article/view/1549.