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@article{MZ_1989__202_1_174109, author = {J\"urgen P\"oschel}, title = {On {Elliptic} {Lower} {Dimensional} {Tori} in {Hamiltonian} {Systems.}}, journal = {Mathematische Zeitschrift}, pages = {559--608}, publisher = {mathdoc}, volume = {202}, number = {1}, year = {1989}, zbl = {0662.58037}, url = {http://geodesic.mathdoc.fr/item/MZ_1989__202_1_174109/} }
Jürgen Pöschel. On Elliptic Lower Dimensional Tori in Hamiltonian Systems.. Mathematische Zeitschrift, Tome 202 (1989) no. 1, pp. 559-608. http://geodesic.mathdoc.fr/item/MZ_1989__202_1_174109/