On flatness of discrete-time nonlinear systemsKaldmäe, Arvo; Kotta, Ülle9th IFAC Symposium on Nonlinear Control Systems 2013 : Toulouse, France, 4 - 6 September 20132013 / p. 588 - 593 https://doi.org/10.3182/20130904-3-FR-2041.00017 Conference Proceedings at Scopus Article at Scopus