“…For instance, in the minimal case, a lot of work had been assembled under the theory of Gottschalk and Hedlund (see [11,17,20]), and the KAM theory (see [2]). In the hyperbolic case, the Liv ˇsic theory has produced a great amount of results (see [6,7,10,13,14,17,19,21,23,24]). Recently the solution to the cohomological equation in the Abelian case has been addressed by some authors as a central problem in the partially hyperbolic dynamical system case (see [16,25]).…”