Samoilenko, Y.S. and Grushevoi, R.V. (2010) “Systems of one-dimensional subspaces of a Hilbert space”, Methods of Functional Analysis and Topology, 16(2), pp. 131–139. Available at: https://zen.imath.kiev.ua/index.php/mfat/article/view/446 (Accessed: 16 December 2025).