1. V. I. Arnol’d, “Poisson Structures on the Plane and Other Powers of Volume Forms,” Tr. Semin. im. I.G. Petrovskogo 12, 37–46 (1987) [J. Sov. Math. 47 (3), 2509–2516 (1989)].
2. V. I. Arnol’d, Mathematical Methods of Classical Mechanics (Nauka, Moscow, 1989; Springer, New York, 1989), Grad. Texts Math. 60.
3. V. I. Arnold, A. N. Varchenko, and S. M. Gusein-Zade, Singularities of Differentiable Maps: Classification of Critical Points, Caustics and Wave Fronts (Nauka, Moscow, 1982); Engl. transl.: V. I. Arnold, S. M. Gusein-Zade, and A. N. Varchenko, Singularities of Differentiable Maps (Birkhäuser, Boston, 1985), Vol. 1, Monogr. Math. 82.
4. H. Cartan, Formes différentielles. Applications élémentaires au calcul des variations et à la théorie des courbes et des surfaces (Hermann, Paris, 1967).
5. J. F. Conn, “Normal Forms for Analytic Poisson Structures,” Ann. Math. 119, 577–601 (1984).