Nawaf, Alaa J., and Akram S.M. Mohammad. “Some Topological Indices and ( Hosoya and Schultz) Polynomial of Subgroup Intersection Graph of a Group Z_r”. Journal of Al-Qadisiyah for Computer Science and Mathematics, vol. 13, no. 1, Feb. 2021, pp. Math Page 120– 130, doi:10.29304/jqcm.2021.13.1.757.