Pradana, Satriawan, et al. “Gutman, Sombor, and Harmonic Indices of Unit Graphs in The Integer Ring Modulo With A Specific Order”. Jurnal Matematika, Statistika Dan Komputasi, vol. 21, no. 3, May 2025, pp. 725-38, doi:10.20956/j.v21i3.43144.