An invariant torus for nearly integrable Hamiltonian systems with infinitely many degrees of freedom

Fröhlich, J., Spencer, T., & Eugene Wayne, C. (2008). An invariant torus for nearly integrable Hamiltonian systems with infinitely many degrees of freedom. In Stochastic Processes in Classical and Quantum Systems (pp. 256–268). Springer Berlin Heidelberg. https://doi.org/10.1007/3540171665_69