Blanchard, Francois, and Mariusz Lemańczyk. “Measure-Preserving Diffeomorphisms With an Arbitrary Spectral Multiplicity”. Topological Methods in Nonlinear Analysis 1, no. 2 (June 1, 1993): 275–294. Accessed July 22, 2024. https://apcz.umk.pl/TMNA/article/view/TMNA.1993.020.