TY  - JOUR
AU  - A. Katok
AU  - D. Bernstein
TI  - Birkhoff periodic orbits for small perturbations of completely integrable Hamiltonian Systems with convex Hamiltonians.
JO  - Inventiones mathematicae
PY  - 1987
SP  - 225
EP  - 242
VL  - 88
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/IM_1987__88_143452/
ID  - IM_1987__88_143452
ER  -