See de la Llave, R.; Marco, J. M.; Moriyón, R. Canonical perturbation theory
of Anosov systems and regularity results for the Livšic cohomology equation.
Ann. of Math. (2) 123 (1986), no. 3, 537–611. See also: Journé, J.-L., A
regularity lemma for functions of several variables, Rev. Mat.Iberoamericana 4
(1988), no. 2, 187–193.
Comments
See de la Llave, R.; Marco, J. M.; Moriyón, R. Canonical perturbation theory of Anosov systems and regularity results for the Livšic cohomology equation. Ann. of Math. (2) 123 (1986), no. 3, 537–611. See also: Journé, J.-L., A regularity lemma for functions of several variables, Rev. Mat.Iberoamericana 4 (1988), no. 2, 187–193.