V. Durai Murugan, R. Seethalakshmi, and P. Namasivayam. “The Lattice Structure of the Subgroups of Order 42 and 48 in the Subgroup Lattices of $2 \times 2$ Matrices Over $Z_{7}$”. International Journal of Mathematics And its Applications 8, no. 3 (September 15, 2020): 141–146. Accessed May 19, 2024. http://ijmaa.in/index.php/ijmaa/article/view/138.