We were interested in proving Siegel's theorem concerning the local conjugacy of rotational dynamics about nonattracting fixed points in the Fatou set. It took until 1997 for Yang's result to be used in an effective way. We must thank K. Astala for pointing out how to make an important step in our argument. Our main results are as follows. We give relevant definitions and a sketch of proof in the next sections.
Quasiconformal mappings are first and foremost mappings of bounded distortion.