Popova, N. D., and O. V. Strilets. “ Criteria for the Existence of Systems of Subspaces Related to a Certain Class of Unicyclic Graphs”. Ukrains’kyi Matematychnyi Zhurnal 73, no. 4 (April 21, 2021): 556 - 565. Accessed April 27, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/6354.