SymокопV. G. and TrofimchukE. P. (1993) “On regularity of linear systems with a degenerate matrix by the derivative”, Ukrains’kyi Matematychnyi Zhurnal, 45(2), pp. 279–286. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/5810 (Accessed: 1September2024).