1. J. MOSER: On Invariant Curves of Area-Preserving Mappings of an Annulus. Nachr. Akad. Wiss. Göttingen, Math.-Phys. Kl. IIa, Nr. 1 (1962) 1–20.
2. J. MOSER: A Rapidly Convergent Iteration Method and Nonlinear Differential Equations II. Ann.Scuola Norm. Sup. Pisa (1966) 499–535.
3. H. ROSSMANN: Über invariante Kurven differenzierbarer Abbildungen eines Kreisringes. Nachr. Akad. Wiss. Göttingen, Math.-Phys. Kl. II, Nr. 5 (1970) 67–105.
4. J. MOSER: MR 42 # 8037.
5. J. MOSER: Stable and Random Motions in Dynamical Systems. Princeton University Press. Princeton, N.J. (1973).