Popova, N. D., and O. V. Strilets. 2021. “ Criteria for the Existence of Systems of Subspaces Related to a Certain Class of Unicyclic Graphs”. Ukrains’kyi Matematychnyi Zhurnal 73 (4), 556 -65. https://doi.org/10.37863/umzh.v73i4.6354.