The stability of the equilibrium position of a Hamiltonian system of ordinary differential equations in the general elliptic case

Arnold, V. I. (2009). The stability of the equilibrium position of a Hamiltonian system of ordinary differential equations in the general elliptic case. In Collected Works (pp. 224–226). Springer Berlin Heidelberg. https://doi.org/10.1007/978-3-642-01742-1_11