Paczko, Dariusz, and Viktor Kulyk. “Some Conditions of Regularity of Linear Extensions of Dynamical Systems With Respect to Selected Variables”. Nonlinear Analysis: Modelling and Control 19, no. 4 (July 7, 2014): 602–610. Accessed May 7, 2024. https://www.journals.vu.lt/nonlinear-analysis/article/view/13657.